Don't buy the camera online. Period. Too many horror stories, too little time.
Call around and visit stores. You'll find that many people in the business are friendly and willing to help. Plus, some local businesses do offer used equipment if you're looking for a cheaper camera.
Amen to that, go to your nearest camera store and hold them in your hands.
Since when you have to carry something like a DSLR around you (and I carry mine EVERYWHERE I go haha) you want it to feel good or else you'll end up leaving it at the house, which is something you should avoid.
Regarding build quality and ergonomics, it all depends on your hands/preference/etc but to me, I thought the Nikon D80 had a better feel for me compared to the Canon 400D ("Rebel" uggh).
Not to mention the other camera brands out there, Pentax/Sony/Olympus/etc. But if you're going into a brand, really check out their lens selection.
Here are some links to help you out...
http://dpreview.com/
http://www.dpreview.com/forums/
http://www.popphoto.com/
http://cameralabs.com/
http://photography-on-the.net/ (Canon Forum)
http://www.nikonians.org/index.php (Nikon Forum + Website Reviews/etc)
If you do end up buying a camera, definitely check out Flickr and DeviantART, although I'm still trying to get the hang of Flickr since I hate my Yahoo account with passion haha.Good luck and do some searching next time xP
P.S. With Nikon being ahead of Canon, currently, that would be the D3 that blows the MKIII out of the water hehe... But that camera costs about couple thousand for the body only, I don't think who's ahead really matters since the OP is going to be buying a two year old camera anyways haha. However, the Canon offers the 17-85mm IS (with a constant aperture) which I hear is amazing, yet so is the 18-200mm VR by Nikon. Like I said, lens selection.
