If you are going to be an 11b card that works with airodump I would recommend that you get a prism2 card because they are very common and widely supported.
Note that, for best compatibility, you shouldn't get a USB card.
Also, don't get the (very common and cheap around here) DWL-122 because it uses a special prism3 card that is not 100% compatible with other prism 11b cards.
To figure out which cards are Prism, try one of these links...
http://www.linux-wlan.org/docs/wlan_adapters.html.gz
http://www.seattlewireless.net/index...rs_5f802_5f11b
http://wiki.personaltelco.net/index.cgi/Prism2Card
Be careful. Vendors will change the chipset and not change the model number of a product.
Qwavel