Our team is rather fond of the
Playstation Eye camera that use to be an accessory for the PS3. It costs less than ten dollars and does 60fps at 480p (also 120fps at 320p, but we've never tried that). This is pretty ideal for vision tracking. The image sensor has ridiculously large photosites, so there is very little image noise to worry about. The only downside is that they don't work on Windows systems very well without a third party driver. On the raspberry pi, it works just fine with OpenCV. You can get them on ebay because they are not made any more.