Save yourself a few hundred and get a Pentax K100D. No, seriously.
* It's about $300 less than the XTi - Use the extra cash to buy a memory card, rechargeable batteries, a bag, and a circular polarizer.
* It's got image stabilization built in - This means every lens you stick on it instantly can be image stabilized. This is something that will cost you ~30% more when buying Canon or Nikon lenses, and it's built into the K100D. You'll get better shots, especially in low light, without a tripod. (It's still good to practice your "still shot taking technique".)
* It's compatible with a shitload of Pentax lenses and the kit lens is better than Canon's - Seriously, you could probably go to a pawn shop and get an old Pentax lens that would perform just as well as a Canon lens three times the cost. And in a very unscientific test, i compared the lenses of both my boss and my own 18-55mm Canon kit lens versus my roommate's Pentax 18-55mm lens. Pentax was a hair sharper out of the camera. It's also built much better, with a range scale and much more precise focusing.
* It's 6.2MP - Boo-fuckin'-hoo. You're not going to print out all your shots out at 13x19, and even if you did, they'd be sharper than if you got the Canon (see the second point) and still look good, especially if you do a little post processing. A sharp 6MP shot > a blurry 10MP shot. Besides, you'll be able to cram a lot more shots on a card and a lot more shots on your hard drive.
i love Canons (<3 my 20D) but the K100D represents a great value in DSLRs that i think it makes a great beginner DSLR. The only reasons i can think of for getting the XTi over the K100D would be if money wasn't an issue, you know someone with compatible lenses/gear, or you really know what you need/want and the XTi has something that the K100D doesn't.