It's a ghetto solution, but it works.  (9-12db gain!)

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<ul>
<li><a href="http://images.google.com/images?gbv=2&hl=en&safe=off&sa=1&q=%22windsurfer%22+antenna+OR+wifi+OR+wireless&btnG=Search&aq=f&oq=&aqi=&start=0">Google Images search</a>
<li>print-out templates
    <ul>
    <li><a href="http://www.freeantennas.com/projects/template/index.html">freetennas.com/.../template1/</a>
    <li><a href="http://www.freeantennas.com/projects/template2/index.html">freetennas.com/.../template2/</a>
        <ul>
        <li><a href="http://www.ljdiaz.com/windsurfer-wifi-booster-poor-mans-wifi/2008/08/24/">article</a>
        <li><a href="http://www.instructables.com/id/Make-a-Wi-Fi-Extender/">article</a>
        <li>heck, buy the <a href="http://www.google.com/products?q=9+dbi+omni+OR+dipole+wifi&aq=f">tallest dipole</a> you can find, and <a href="http://www2.zansstuff.com:5190/images/windsurfer.jpg">double-up the Windsurfer</a>
        </ul>
    <li><a href="http://binarywolf.com/249/diy-parabolic-reflector.htm">binarywolf.com</a>
    </ul>
<li>commercial products
    <ul>
    <li><a href="http://www.tritium.co.uk/Flatennaroot.htm">Flatenna</a> from Tritium ($15 shipped)
    </ul>
</ul>