i have one of the original intel imacs, but the wireless adapter has gotten flakey. is it possible to replace it by using an external usb wifi adapter of some sort? recommendation of a compatible product?

It is indeed possible however your problem is finding one that is on the market readily avalaible and compatible too

At this link there is a list of compatible external and interal wi-fi devices where you can see which work: http://forums.dealmac.com/read.php?4,2604929 (2nd post down)

Searching through it looking for the best one I would reccomend is avalaible at Amazon here from a company a trusted company called MacSense: http://www.amazon.com/Macsense-AeroLite-802-11g-54Mbps-Adapter/dp/B000M801WC/ref=sr_1_2?ie=UTF8&m=A2U84PQRTYPMC7&s=generic&qid=1286872439&sr=1-2