The DLink cameras are pretty cheap, and the hardware is actually surprisingly decent. The software, though(at least as of last summer, when I set up a bunch of them, and the surveillance backend hardware) is unbelievably horrible. It looks like something that would be bundled with a cheap consumer scanner, and works about half as well.
If you just want to use the onboard web server in the camera to manually check up from time to time(or send pictures to some network location based on motion events) they aren't bad, at least for the money; but if you want a serious tape-to-server setup Run Screaming As Fast and Far As Possible.