The keyring camera from Digital Dream called L'Espion is another with a good low light capability extending into the IR end of the spectrum, the case is of the snap fit variety and yields to a screwdriver with a bit of brute force.
Cheap digital cameras / webcams to avoid... anything marked 'Oregon Scientific'
the cases are generally held together with screws and opening them up is painless but the image quality is awful (far worse than keyring cam) and the driver software unstable on WinXP. At least that has been my experience, I may of just had a bad one from the batch.
Like many night owls on the web I found that using a webcam after dark involved grabbing every desk lamp I could find to hand and burning my retinas.These days I use a Phillips CCD camera connected to the PC using a TV tuner card (its got a spare input for composite video). The camera came from a local pawnbroker franchise, I swear they must of thought it was a dummy one as it only cost me £5. Came complete with an adjustable C mount lens with auto iris and works a treat from just the glow of the monitor screen.