If you are looking for a good little camera to use in computer vision applications, like multi-touch tables etc, the PS3 Eye has a very good quality/price relation(3 times cheaper then other cams with similar results), It works on Linux, OSX and Windows.

Unfortunately the support that ships with the camera only allows the camera to stand up vertically which is not very handy for multi-touch tabletops and other applications where you want the PS3 Eye to point upwards.
Thanks to the Makerbot, you can now print a support to hold your PS3 Eye horizontally and avoid having to take the whole thing apart.
Read more about this wonder-full little cam --> bit.ly/13LVPH
It also has its own wikipedia page --> en.wikipedia.org/wiki/PlayStation_Eye