Depends what you consider cheap
I put together a system on my home automation PC using an
AVerDiGi - AVerDiGi NV3000 board. It supports 4 cameras (4 analog or 1IP/3 analogs), you can add more boards to add more cameras, has a Web app, standalone app as well as a PDA app. It also supports numerous cctv controllers/switchers to support PTZ which is pretty impressive. For awhile I had it connected to a Panasonic IP camera and it natively handled the Pan/tilt which was neat.
People are usually pretty impressed when they see my streaming video from my cameras on my cell pda phone live. It has a video out that can either go direct to a TV, or I bought a modulator so it had a TV channel so I can feed it easier. Only complaint is it's a bit finnicky with motherboards and doesn't like my AMD board much (they recommend Intel boards.)
I've picked up a few cameras from different sources, my best advice is spend as much as you can on the cameras and keep an eye on the specs. You can definitely tell the difference between a cheap one and an expensive one for image quality. After wasting money on <$99 cameras I picked up a few mid-grade ones and much happier with the results. Also the all in one unshielded cables can often add nasty noise, so if you need to run power and video, get some decent shieled siamese cable.
Just my .02, I'm no where near an expert but like to play with this stuff
-Mike