You can get either an All-In-Wonder Radeon 32 MB video card which has a TV tuner built-in, or get a GeForce 2/3 video card and buy a PCI TV tuner card seperate. Hauppauge makes good TV tuner cards.
If you're just looking to hook your TV to it, get either a Radeon with VIVO or a GeForce 2/3 with S-Video out.