﻿<?xml version="1.0" encoding="utf-8"?>
<InstanceReport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.2.0.7</Version>
  <hasSegments>false</hasSegments>
  <ReportName>Share Repurchase Plan</ReportName>
  <ReportLongName>0210 - Disclosure - Share Repurchase Plan</ReportLongName>
  <DisplayLabelColumn>true</DisplayLabelColumn>
  <ShowElementNames>false</ShowElementNames>
  <RoundingOption />
  <HasEmbeddedReports>false</HasEmbeddedReports>
  <Columns>
    <Column>
      <LabelColumn>false</LabelColumn>
      <Id>1</Id>
      <Labels>
        <Label Id="1" Label="6 Months Ended" />
        <Label Id="2" Label="Jun. 30, 2010" />
      </Labels>
      <CurrencyCode>USD</CurrencyCode>
      <FootnoteIndexer />
      <hasSegments>false</hasSegments>
      <hasScenarios>false</hasScenarios>
      <Segments />
      <Scenarios />
      <Units>
        <Unit>
          <UnitID>USD</UnitID>
          <UnitType>Standard</UnitType>
          <StandardMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema>
            <MeasureValue>USD</MeasureValue>
            <MeasureNamespace>iso4217</MeasureNamespace>
          </StandardMeasure>
          <Scale>0</Scale>
        </Unit>
        <Unit>
          <UnitID>USDEPS</UnitID>
          <UnitType>Divide</UnitType>
          <NumeratorMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema>
            <MeasureValue>USD</MeasureValue>
            <MeasureNamespace>iso4217</MeasureNamespace>
          </NumeratorMeasure>
          <DenominatorMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema>
            <MeasureValue>shares</MeasureValue>
            <MeasureNamespace>xbrli</MeasureNamespace>
          </DenominatorMeasure>
          <Scale>0</Scale>
        </Unit>
        <Unit>
          <UnitID>Shares</UnitID>
          <UnitType>Standard</UnitType>
          <StandardMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema>
            <MeasureValue>shares</MeasureValue>
            <MeasureNamespace>xbrli</MeasureNamespace>
          </StandardMeasure>
          <Scale>0</Scale>
        </Unit>
      </Units>
      <CurrencySymbol>$</CurrencySymbol>
    </Column>
  </Columns>
  <Rows>
    <Row>
      <Id>2</Id>
      <Label>Share Repurchase Plan [Abstract]</Label>
      <Level>0</Level>
      <ElementName>us-gaap_TreasuryStockNoteDisclosureAbstract</ElementName>
      <ElementPrefix>us-gaap</ElementPrefix>
      <IsBaseElement>true</IsBaseElement>
      <BalanceType>na</BalanceType>
      <PeriodType>duration</PeriodType>
      <ShortDefinition>No definition available.</ShortDefinition>
      <IsReportTitle>false</IsReportTitle>
      <IsSegmentTitle>false</IsSegmentTitle>
      <IsSubReportEnd>false</IsSubReportEnd>
      <IsCalendarTitle>false</IsCalendarTitle>
      <IsTuple>false</IsTuple>
      <IsAbstractGroupTitle>true</IsAbstractGroupTitle>
      <IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow>
      <IsEquityAdjustmentRow>false</IsEquityAdjustmentRow>
      <IsBeginningBalance>false</IsBeginningBalance>
      <IsEndingBalance>false</IsEndingBalance>
      <IsReverseSign>false</IsReverseSign>
      <PreferredLabelRole />
      <IsEPS>false</IsEPS>
      <FootnoteIndexer />
      <Cells>
        <Cell>
          <Id>1</Id>
          <ShowCurrencySymbol>false</ShowCurrencySymbol>
          <IsNumeric>false</IsNumeric>
          <IsRatio>false</IsRatio>
          <DisplayZeroAsNone>false</DisplayZeroAsNone>
          <NumericAmount>0</NumericAmount>
          <RoundedNumericAmount>0</RoundedNumericAmount>
          <NonNumbericText />
          <NonNumericTextHeader />
          <FootnoteIndexer />
          <hasSegments>false</hasSegments>
          <hasScenarios>false</hasScenarios>
          <DisplayDateInUSFormat>false</DisplayDateInUSFormat>
        </Cell>
      </Cells>
      <OriginalInstanceReportColumns />
      <ElementDataType>xbrli:stringItemType</ElementDataType>
      <SimpleDataType>string</SimpleDataType>
      <ElementDefenition>No definition available.</ElementDefenition>
      <IsTotalLabel>false</IsTotalLabel>
    </Row>
    <Row>
      <Id>3</Id>
      <Label>Share Repurchase Plan</Label>
      <Level>1</Level>
      <ElementName>us-gaap_ScheduleOfTreasuryStockByClassTextBlock</ElementName>
      <ElementPrefix>us-gaap</ElementPrefix>
      <IsBaseElement>true</IsBaseElement>
      <BalanceType>na</BalanceType>
      <PeriodType>duration</PeriodType>
      <ShortDefinition>No definition available.</ShortDefinition>
      <IsReportTitle>false</IsReportTitle>
      <IsSegmentTitle>false</IsSegmentTitle>
      <IsSubReportEnd>false</IsSubReportEnd>
      <IsCalendarTitle>false</IsCalendarTitle>
      <IsTuple>false</IsTuple>
      <IsAbstractGroupTitle>false</IsAbstractGroupTitle>
      <IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow>
      <IsEquityAdjustmentRow>false</IsEquityAdjustmentRow>
      <IsBeginningBalance>false</IsBeginningBalance>
      <IsEndingBalance>false</IsEndingBalance>
      <IsReverseSign>false</IsReverseSign>
      <PreferredLabelRole>verboselabel</PreferredLabelRole>
      <IsEPS>false</IsEPS>
      <FootnoteIndexer />
      <Cells>
        <Cell>
          <Id>1</Id>
          <ShowCurrencySymbol>false</ShowCurrencySymbol>
          <IsNumeric>false</IsNumeric>
          <IsRatio>false</IsRatio>
          <DisplayZeroAsNone>false</DisplayZeroAsNone>
          <NumericAmount>0</NumericAmount>
          <RoundedNumericAmount>0</RoundedNumericAmount>
          <NonNumbericText>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note 10 - us-gaap:ScheduleOfTreasuryStockByClassTextBlock--&gt;
   &lt;div style="font-family: 'Times New Roman',Times,serif; margin-left: 0in; "&gt;
   &lt;div style="margin-top: 10pt"&gt;
   &lt;table width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt; text-align: left"&gt;
   &lt;tr valign="top" style="font-size: 10pt; color: #000000; background: transparent"&gt;
       &lt;td width="3%" nowrap="nowrap" align="left"&gt;&lt;b&gt;10.&lt;/b&gt;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;
   &lt;div style="text-align: justify"&gt;&lt;b&gt;Share Repurchase Plan&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;/table&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;On November&amp;#160;14, 2008, the Company announced that its board of directors approved a share
   repurchase plan authorizing the Company to repurchase, from available capital, up to $20
   million of the Company&amp;#8217;s outstanding common stock from time to time through November&amp;#160;13, 2009.
   The timing and amount of any share repurchase under the share repurchase plan were determined
   by management of the Company based on market conditions and other considerations, and
   repurchases may be effected in the open market, through derivative, accelerated repurchase and
   other privately negotiated transactions and through plans designed to comply with Rules&amp;#160;10b-18
   or 10b5-1(c) under the Securities Exchange Act of 1934, as amended. The share repurchase plan
   did not require the Company to acquire any specific number of shares and may be temporarily or
   permanently suspended or discontinued by the Company at any time. A committee of the board of
   directors reevaluated the operation of the plan each fiscal quarter.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;During November and December&amp;#160;2008, the Company sold written put options of its own shares as
   part of the Share Repurchase Plan, those put options were not exercised at the expiration date
   and for that reason, during the first quarter of 2009, the Company recognized a gain of
   $185,000.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;The Company accounted for its written put options as derivative instruments and measured them
   initially and subsequently at fair value. The liabilities associated with these derivative
   instruments were recorded at fair value in current liabilities in the consolidated balance
   sheet.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;During March&amp;#160;2009, the Company sold written put options of its own shares. The following table
   summarizes the written put option transactions made in the first quarter of 2009:
   &lt;/div&gt;
   &lt;div align="right"&gt;
   &lt;table style="font-size: 10pt; text-align: left" cellspacing="0" border="0" cellpadding="0" width="96%"&gt;
   &lt;!-- Begin Table Head --&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td width="77%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="3%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="9%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2" style="border-bottom: 1px solid #000000"&gt;&lt;b&gt;Total&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Head --&gt;
   &lt;!-- Begin Table Body --&gt;
   &lt;tr valign="bottom"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff; padding-top: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;Number of Shares
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;226,000&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="padding-top: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;Premium
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;302,997&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff; padding-top: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;Average Price
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;1.34&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="padding-top: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;Commissions and other fees
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;(6,782&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff; padding-top: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:15px; text-indent:-15px"&gt;Cash received
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;296,215&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Body --&gt;
   &lt;/table&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;These put options were not exercised at the expiration date and for that reason, during the
   first half of 2009, the Company recognized a gain of $302,997.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;No additional written put option transactions were made during the three-month period ended
   June&amp;#160;30, 2009. As of June&amp;#160;30, 2009 there was no written put options transaction outstanding.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;Those derivative financial instruments were not accounted for as hedges and, therefore, the
   change in the fair value of these instruments was recorded in the income statement as interest
   income and other financial gains.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt; margin-left: 4%"&gt;No written put option transactions were made during the three-month period ended June&amp;#160;30, 2010.
   As of June&amp;#160;30, 2010 there is no written put options transaction outstanding.
   &lt;/div&gt;
   &lt;/div&gt;
</NonNumbericText>
          <NonNumericTextHeader>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note</NonNumericTextHeader>
          <FootnoteIndexer />
          <hasSegments>false</hasSegments>
          <hasScenarios>false</hasScenarios>
          <DisplayDateInUSFormat>false</DisplayDateInUSFormat>
        </Cell>
      </Cells>
      <OriginalInstanceReportColumns />
      <ElementDataType>us-types:textBlockItemType</ElementDataType>
      <SimpleDataType>textblock</SimpleDataType>
      <ElementDefenition>This element may be used to capture the complete disclosure pertaining to an entity's treasury stock, including the average cost per share, carrying basis for each class of treasury stock, description of share repurchase program authorized by an entity's Board of Directors, the treatment of the purchase price in excess of the current market value, number of shares held for each class of treasury stock, and other information necessary to a fair presentation.</ElementDefenition>
      <ElementReferences>No authoritative reference available.</ElementReferences>
      <IsTotalLabel>false</IsTotalLabel>
    </Row>
  </Rows>
  <Footnotes />
  <NumberOfCols>1</NumberOfCols>
  <NumberOfRows>2</NumberOfRows>
  <HasScenarios>false</HasScenarios>
  <MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel>
  <SharesRoundingLevel>UnKnown</SharesRoundingLevel>
  <PerShareRoundingLevel>UnKnown</PerShareRoundingLevel>
  <HasPureData>false</HasPureData>
  <SharesShouldBeRounded>true</SharesShouldBeRounded>
</InstanceReport>
