Avoid buying cheap-o security cameras, such as ones from Swann, Q-See, etc. at all costs. If you are lucky enough to find printed specs on the package, you'll notice that they have high noise levels, high lux levels, and low resolutions, all of which translates to a garbage picture and endless false-positives with motion capture software.
The Swann I tried today simply died after 10 minutes of use. Blank, no picture.
If you pay a bit more, you can get a much higher quality camera from Lorex. I have a VG1030R mounted outdoors. Solid metal construction, and it delivers a clean picture at a decent resolution for motion capture in all but the lowest light situations. Sure, it isn't a 525 line CCTV, but for $79 at Fry's/Outpost.com, it is a hard value to beat.