If you have $1500 to spend, I'd go with the Canon 40D. I have the 30D and absolutely love it, and the 40D has only improved. If you are looking to spend less, my sister just got the Canon Rebel XTi and has been impressed with the picture quality. I'd recommend reading user reviews on cameras to get an idea...then go to a photography shop and 'hold' the camera. I thought I wanted a Nikon, but it just didn't feel right in my hands. For some reason the Canon did.
Flickr has a nice camera review site. http://www.flickr.com/cameras/