I found this nifty guide by "Th !e.FaLconO6" on building a nice computer for the right price. At version 0.8, it was last updated June 2nd, 2010.

2-18-2012 - UPDATE!
You can find an updated version of this guide here:
http://i1002.photobucket.com/albums/af150/The_FalconO6/CurrentLogicalPCBuyingGuide/Guide.png

More Stuff here too:
http://s1002.photobucket.com/home/The_FalconO6/index

Thanks Internet!

I was recommended this brand of wireless card about a year ago. Compatible with Windows/Linux/UNIX, this is the type of card you would use for rigorous wifi analyzing or wardriving.

Ubiquiti Wireless Card SR71C 802.11N/G/B/A w/ 2 Antenna Jacks & Clip-on Antennas
http://www.data-alliance.net/-strse-137/Ubiquiti-SR71C-SR71-dsh-C-MIMO/Detail.bok

Ubiquiti SR71X Wireless-N Card for Express Card Slot. Has Antenna Jack. 802.11N/G/B/A
http://www.data-alliance.net/-strse-104/Ubiquiti-SR71X-300mW-802.11N/Detail.bok

You can find more products on their website (http://www.data-alliance.net). They also sell these on eBay. Just search Ubiquiti.