My advice is to buy what is known as a 'Scan Converter'. These are little boxes that transmorgify the standard VGA signal used by computer monitors to composite or svideo used by televisions (and sometimes YUV component). You plug the scan converter into your video card and then both your TV and monitor into the scan converter.
The advantage of this is that you can run nearly any resolution on your monitor and have it scaled automatically to a resolution that works on your TV. Otherwise, you'll have to run your monitor at a ridiculously low resolution when mirroring to the TV. Also, most video cards will cut your video memory in half and use half for the TV even if it is mirroring the image on the monitor. With a scan converter, you'll have none of these issues and it will still work when you upgrade to your next machine.
You'll also get the benefit of hardware controlled fine tuning for image placement, overscan, and sharpness.
Just make sure the scan converter is supports the highest resolution you use. Currently, I've got one that supports the 1280x1024 of my LCD monitor. My radeon 8500 is thus running on a full 64 megs for the primary display and to use the TV, I only have to turn in on and switch to input 2.