This Wifi card is great! Costs under $14.00 USD delivered from eBay and works with no interaction in Ubuntu (Jaunty).
The card is a standard PCI-type.
This is the first network adapter I have used that you simply plug in and it works as if it is created especially for Linux. It even works with Windows, but you have to install alot of software to make it work (unlike Ubuntu which just requires the card be installed).