One that is getting some great reviews is the D-Link DSC-350 USB Digital and Webcam. Not only does it have 640 x 480 Resolution it will also take upto 145 still images aas a regular camera or 4.5 minutes of video. Outpost.com has this one for $69.95, although it will be a backorder it is worth the price and wait. Link Below
http://shop1.outpost.com/product/3166720/#detailed