That camera was incredible in that it took great images, even at high ISO speeds. It does much better than the 5D in terms of eliminating noise at high ISO speeds.
For this reason I can recommend the newer version of that model, Canon EOS Rebel T3i.
A cheaper alternative to the T3i is the Canon EOS Rebel T3, which is several hundred dollars less than the T3i. The T3i has 18MP while the T3 has 12MP. Both cameras, however, can be used for just about everything from shooting stock photos to selling the at Fine Art America.
Many of my stock photos were taken with the Rebel XT so they, too, are perfectly good. The Canon Rebel XT is the cheapest Rebel at $277 (used). A new one is over $1000!
If you have the camera already, pick up David Busch’s Canon EOS Rebel T3i/600D Guide to Digital SLR Photography (David Busch Camera Guides)
(he’s good; I wrote a book with him).