I also say stick with Canon. Nikon is also a good SLR but it seems to me that there are more items readily available for Canon. I don't think that a Rebel is a horrible first choice but they're not very rugged at all. I started out with a Rebel and then after i got used to it, upgraded to the then new Canon 20D. The Prosumer 20D which much more of a camera, felt better, was built better, etc. My sis has an XTi and it's OK for a first camera but i would never go back now. The latest version in the prsoumer lineup is a 40D. The 30D was after mine.
I highly recommend whatever is the newest in the prosumer line of Canon's.