you could look at the LQ wiki
, but it doesn't offer too much info(presently) except about which drivers should work.
I have an nvidia card so I can't be too specific, but configuration involves setting up second device, monitor, and screen sections in xorg.conf for the TV. There are vendor/driver specific options that are entered in the device section to force SVIDEO/composite, NTSC/PAL, and to tell X a TV is plugged in(I'm not mentioning them specifically as they're different for ATI/nvidia). Otherwise it's not much different than setting up dual monitors.
here's a monitor section for your TV that should work fine (provided you have a regular analogue TV set):
HorizSync 30 - 50
You should be able to configure a serverlayout with 2 screens as your desktop, and you can also, (with some difficulty perhaps), configure a serverlayout with just your monitor and launch a second X server on vt8 to the TV, on demand from the first for watching videos (I just got this working at long last myself and it's great - launch an AVI from my monitor, the TV comes up and starts playback as the monitor goes into standby). Anyway, I'm way past the point you're at right now. Do some googling, or perhaps investigate the documentation that comes with the driver your using (I have no idea about the quality of ATI's docs though). Once you've got working device, monitor, and screen sections, I'd be happy to elaborate on different serverlayout configs (which should be vendor/device independent).
Sorry I don't have more specific info for ya.