What is your budget?

If you are not sure about your budget (my impression is that you have the money, but not yet sure how much you are willing to spend), get 450D (aka XSi) or 50D (bigger and more functions) + Canon 18-200mm IS lens.

After a year or so, you will know if you want more for your photography. If no, 450D or 50D will be good enough. If yes, this initial package will be your backup or travelling photography (18-200mm is a very convenient lens: small and powerful zoom).

Nikon lenses are significantly more expensive once you decide to move upward.