I personally prefer Nikon having owned a Coopix 995, a D80 and now a D300.
In your price range you could get a D40 or a D60. See.
A better idea might be to look for a used D80 with lens that someone who recently upgraded to a d300 or d700 might have for sale.
If you seriously want to get started with a DSLR (digital single lens reflex), I'd ante up and get a D300.
I am sure that Canon makes fine camera's in similar price ranges too.
I can tell you that I recently upgraded from a D80 to a D300 and I am glad I did. The D300 is allot of camera though and it takes some study time to understand how to use it effectively. It's probably not a good starter camera unless you are really committed to learning photography.
We do all our photos with a Nikon D80, and love it... takes amazing pictures of coral with a macro lens and tripod. Like the others said, it's hard to go wrong with Nikon or Cannon!