Internet Access

For WiFi: 

• for single PC: http://www.engeniustech.com/datacom/products/details.aspx?id=154 
• For bridging to a local WifI http://www.engeniustech.com/datacom/products/details.aspx?id=230 
• Antenna for above: http://www.engeniustech.com/datacom/products/details.aspx?id=215 
• Buy here: 
• http://www.keenansystems.com/store/catalog/product_info.php?cPath=2&products_id=224 (Bridge/AP, $150),
• http://www.keenansystems.com/store/catalog/product_info.php?cPath=3&products_id=67  (pigtail, $11)
• http://www.keenansystems.com/store/catalog/product_info.php?cPath=3&products_id=255 (antenna, $30).
• Keenan systems also offers a package with the above, but the package is more expensive ($233)
• A possibly cheaper solution: ubiquiti networks http://www.ubnt.com/products/ns2.php 
• outdoor-rated cable: http://www.cat5ecableguy.com/inc/sdetail/14224

Mac and boat electronics

MacENC is pretty much what you need for charts/navigation software.  

Pair with a USB antenna ( http://www.gpsnavx.com/MacENC/index.php?page=Compatibility , scroll to the bottom).  Make sure you get the drivers MacENC recommends, the prolific driver or read here: http://www.gpsnavx.com/help/connectinggps.htm

For more info, check out the mac sailing forums.  For charts, look for Jim's sailing server.

Decent thread on a Mac Mini on-board! Seems people are also installing these in cars (gooogle it.)