Analogue cameras

Use standard analogue CCTV cameras.

Quad processors

If you are using more than two or three cameras, you will probably want to connect them through one or more quad processors.

FireWire inputs

Use FireWire DV inputs such as the Canopus AVDC 55 to connect quad processors or single cameras to your Mac. You may need a FireWire hub if your Mac doesn't have enough free FireWire ports.

Cabling

You will need coaxial cabling for each camera and quad processor output, and a "BNC->RCA" adapter to connect to each FireWire input.

Mac

Any Mac with a FireWire port can run this system. You will need about 20 GB of free disk space per camera.