I just purchased a Nikon D5100. In the running for the price range was Canon T3i and Sony A55 which seems to the case with most of us looking in that price range. After reading through reviews, forums, and seeing the video Gordon did compairing the Nikon and Canon (super video review btw), it can get even more confusing. As a newb to DSLR cameras, you want to get the best for your budget. Ultimately, each camera brand will bring something slightly different to the table. For ex: the Sony A55 brings a super fps which is unmatched by others in the running, but battery life isnt as long and the digital view finder might be a turn off. It is also a smaller camera, and for someone with large hands, it might not feel comfortable. The Canon is a larger camera than the Sony and Nikon on hand grip feel.
Here are my tips to avoid stressing out over which one to buy: Go to the store and hold them FIRST! I guarantee you will narrow it down once you hold them, get a sense for hand feel, how body position feels, and check out the LCD left vs bottom hinge, and also the view finder (digital vs traditional). Camera feel is extremely personal, and you need to be happy with how it feels regardless of reviews or opinions on the forum. Dont ask the opinion of the guy working there. It will only confuse you more, and for some it will make you feel like you must buy the one they recommend.
If you are still torn after holding them, check out your local camera shop (not best buy, but a real dedicated camera shop) to see if they have a rental program and rent them for the weekend.
If you are getting a camera because you want to start a hobby, make a list of what you want to realistically use the camera for. Is video important or is fps higher on the list? Canon and Nikon are neck and neck as far as photo quality. My thoughts are, if video is that important, get a dedicated video camera. If you are serious about taking up photography as a hobby, your camera will become an extension of you. If you really arent in to going manual, but want to take really nice photos of the family, then save yourself the trouble and just buy a nice quality point and shoot like looks like a DSLR...you can take great photos and tweak them in photoshop, but save yourself a few hundred bucks. The bottom line is, you arent going to make a bad choice between the top brands. You just need to pick one that will suit your needs (easier menu navigation for a newb--Nikon, great all around camera that feels more semi pro in menu options--Canon or higher fps--Sony, etc), and feel confident in your decision.
Honestly, I went to buy the Canon. I felt the Nikon had too many "fun" features that I wasnt interested in for the minimal added cost. In the end, after a few years of wanting a canon rebel, and all the reading on features and narrowing it down to my Canon T3i, I walked out of the store with the Nikon because it fit me like a glove. I ended up getting it for the same price as the canon, 2 lenses, a free bag, etc. I'm happy with it and dont regret it at all.