I still love my NIkon D-40 and I haven't had to charge my battery in over four months
. The first time I used it I manages somewhere in the 650-750 shot range with using the flash.
I would suggest you really look at battery life when your deciding, I ditched my Olympus E-10 camera cause it took forever to boot so I constantly missed shots, and then the battery was always dieing at the worst possible moments.
I also didn't get the Cannon Rebel since it was an "on rails" prosumer camera that had settings but no control. It might have changed since I've not really looked into cameras over the last 2 years since I'm set.
The only issue with the Nikon D-40 is there is no focusing motor in the body so you can't use old lenses it can only auto focus with lenses that have the motor in them. You can always get a heavier Nikon camera that has the motor in the body and get use out of your current set of lenses.
As has been suggested BH Photo Video is probably the best online source for purchasing cameras unless you run across an uber deal somewhere else. Be careful of the scam stores research any unknown store before buying, I saved myself alot of grief by doing that.
New Digital Cameras | B&H Photo Video
Used Used Digital Cameras | B&H Photo Video
This is one of the best review site I've read (hopefully you've already found it but just incase) DCRP Review: Nikon D40 DCRP Review: Canon Digital Rebel XTi DCRP Review: Canon Digital Rebel XT