Well, I can't say its the best, but I'm using the D-Link DWL-650 card in mine, as are a number of other folks.
I have to say that it was just about as PnP as you can get. I follwed the instructions included with the Prism driver linked to from the network tab of the http://www.geocities.com/epodsfiles web site.
This required the software to be installed via activesync, the card to be popped in, and the name of the network card driver to be typed into a dialog box. Its worked great from that point on, and I'm using it with the D-Link DWL-1000 Access Point. They are set to work on the same channel right out of the box.
The cost is about $125 for the card, I believe, and about $250 for the access point.