I just joined, and the out-of-date FAQ I received upon arrival here states that there are no other hacked EOS digicams. I've just gotten my first DSLR, a Rebel XT (350D) and I found a forum where they discuss a CF-card based hack, which can be read into the camera upon booting and allows lots of added features, like spot metering, custom color temp, exposure bracketing, "safe-shift" in Av and Tv(?), total shutter counts, time-lapse settings, ISOs up to 3200, etc. Very different than the 300D hacking, because of the different OS the newer cameras run (different architecture, too, ARM vs X86.)
More info here: http://chdk.wikia.com/wiki/350D
I was considering an XTi, and found that that camera has an even more-developed hack (I found it first.) I can't remember where it is exactly, but I remember it is called "400plus", so doing a google search on "canon 400d 400plus" (without the quotes) should get you a lot of info.
I only recently got interested in photography when I helped my teenage daughter buy a Rebel T3 (1100D) for a really sweet deal ($325 with kit lens.) She's in a photography class given through a downtown studio, and has gotten very interested - and learned that her pics looked much better when borrowing an instructor's DSLR (vs. her "nice" Kodak compact, on full auto, of course.)
I just got the 350D in non-working condition (Err 99) for $20. I located a copy of the factory repair manual for the camera (the one some guys are trying to sell on eBay and through other online stores) but it is somewhat disturbing to read, every time they remove a part, they show the wires that need to be un-soldered(!) - I saw some YouTube videos and I didn't see any unsoldering going on, so I guess that's just the way the factory likes it. They can test the sub-assemblies and replace as needed once the camera is completely apart.
By the way, if anyone has found a copy of the repair manual for the 400D, I'd really like to have one, as I'm interested in finding one of these cameras if the price is right.
Scott in Penfield NY