You don't need any special equipment if you're just starting out with astrophotography. So forget about a telescope and an equatorial mount (to counter the earth's rotation) just for now, it's complicated enough already without those things ;).

Besides the moon you can take wide field shots of the night sky with your 20D and a normal lens and tripod. I suggest you use a lens that has a large aperture (e.g. the 50mm F1.8) since you want to capture as much light as possible.

On a fixed (normal alt/az) tripod you could try photographing:

• constellations
• star trails

Because the rotation of the earth the stars appear to move. Therefore you need to limit the exposure time unless you want to photograph star trails. There are some guidelines to determine the maximum exposure time on the Astropix site (I have a calculation somewhere as well, I'll try too look it up for you). It's advisable to take multiple photo's of the sky and stack these. This will improve the signal/noise ratio considerably. DeepskyStacker is an easy (and freeware) tool to help you stacking your images. The images do not have to be aligned. DeepskyStacker will do the alignment and registration for you. If you find DeepskyStacker too limited you can also try IRIS. This tool is not so user friendly but it offers many more options than DeepskyStacker.

Once you've mastered astrophotography with a fixed tripod and a normal lens you can consider an equatorial mount and a telescope. Since a telescope will magnify the image so much you will need an equatorial mount otherwise the stars and galaxies will move out of your frame in seconds. Buy the best equatorial mount you can afford. I had a Orion Skyview Pro mount which was not so well performing so it was useless for serious astrophotography. The Losmandy GM-8 and Vixen Sphinx mounts are far better. If you only want to use the camera the Kenko Skymemo would be a good solution.

There are many different telescopes you can choose (refractor, reflector, catadioptics) and each has their pros and cons (could be another post ;). I had an Orion ED80 refractor and was very happy with it. To connect your camera to a telescope you'll need a photo adapter like this one.

Last but not least: if you live in an area with lots of light pollution you can consider buying a light pollution filter. I can recommend the front filters from Hutech. These filters are placed in the camera body and therefore work with many types of lenses and telescopes.

Clear skies! (this is the standard astrophotographer greeting :)

EDIT:

As promised: Here's a link to a Google spreadsheet where you can calculate the maximum exposure time without trailing stars. You need to provide 2 numbers: camera crop factor and focal length of the lens. The final parameter is the declination of the celestial object (already available in the table in 5 deg steps to get a rough idea).