If you want to use the TV as a monitor you will need a video card with TV Out feature. Both ATI AllInwonder and NVidea are good choices. ATI has long been the leader in TVOut, however,
Cards like the ATI AllInWonder also come with TV Tuner, so that you can route all your TV signals through your PC and effectively use you PC as TV tuner, digital TV recorder (like Tivo) and monitor.
That being said, the resolution on a TV is very poor (worse that 640x480) and not all color components are in full resolution. consider getting an inexpensive monitor in stead.