CRAP i just wrote a whole damn essay on stuff about photo and the 30D, then hit back on my browser and..... poof!
Anyway, I'm in school for photography at RIT, and the 30D is my workhorse. 20D or 30D doesn't really matter, as they're basically the same camera, although the big LCD on the 30D is a nice touch and one that I appreciate often.
Anyway, check keh.com , they're really great, I've bought multiple lenses and cameras from them and they're the biggest used camera dealer around. Buy whatever's cheapest, as long as it's not rated "Ugly". The "Bargain" stuff is a really good value, cosmetically not perfect, but functionally as good as new.