http://www.dpreview.com/
Check out this site and pay close attention to the image cross comparisons and decide which DSLR works best for what you want to do.
My first foray into the digital realm was a Nikon D100. Once Canon came out with the 5D, I sold all my Nikon equipment and went all in on Canon (now have both the 5D and 5D MK 2).