i've owned many different webcams.. the best image is from the 3com webcam (not the lite model). discontinued but still available on E*ay.
intel pc pro webcam is excellent (excellent image/clarity/contrast/fps) (intel is discontnuing this! why all the best webcams are being discontinued i don't know)
you can find this occasionally for about $30.00 after rebate. check dell peripherals and intel site for proces/rebate - or fry'sthe webcams typically require a usb port to function
el super cheapo route - but best image resolution possible short of dedicating an actual digital camera to be your webcam - get a Snappy version 3 or 4 (used off E*ay) - video frame grabber - you can get these really really cheap, a few bucks, and hook up a old camcorder you've got laying around. the snappy can grab a frame of about 1 megapixel, and using some freeware you can ftp this to your server and have an automatically updating webcam. good option if you like to tinker, and have an old camcorder (doesn't everyone?) PM if you need more specifics