Review my web app, CraigUpdate.com
sev: Not bad at all.  I had the same idea and was about to implement it, but you beat me to it.  The only suggestion (small one) that I have, is that once you register for the first time, and it suggests you register again for another keyword, the city drop-down menu changes back to default.  Generally speaking (although not always the case), the requester would probably choose the same city for every keyword search.