Bethany,
I'm a newb, but here's my 2 cents.
I started with a Canon PowerShot back in June...I loved it (I still do, but it's not an SLR). So, naturally, like most folks are saying here, I immediately looked at the Canon Rebel XT (350). It felt very small and light in my hand, so I looked at the 20D...and I fell in love. That was the camera I wanted. This dude at my sister's wedding had one, and he let me play with it. This just reinforced my desire for the Canon 20D.
I posted a similar thread, as I think everyone new to photography and TPF does

. My understanding is that you can't go wrong with a Canon or a Nikon...both are great cameras and great companies. I also learned from here and from talking to the photographer here at work, that I would be better off going with a less expensive body and using the rest of the money for lenses.
Because the folks that I know personally on the forum (save Kelox) all use Nikon, and because the photog here at work uses Nikon, I started looking at the D50, the D70, and the D70s. Without getting into the details, I narrowed my choice down to the Canon 20D and the Nikon D70s. What tipped the scale for me was 2 things: the D70s was a little cheaper than the Canon (again following the logic that I should spend my money on glass and not body), and my brother-in-law had a 35mm Nikon with 2 lenses that would fit and work with the D70s. In the end I went with the D70s, but I don't begrudge anyone who has a Rebel or a 20D.
Ultimately, like others have said, you need to play with them. Go to the store and hold them in your hand. This is why I settled on the D70s vs. the D50 and the 20D vs. the Rebel. Also, one of the most important things that I have learned here on TPF is that it's NOT the camera or the lenses; it's the photographer.
Whether you get a Canon or a Nikon, you'll be happy, and that will reflect in your desire to use it, which will get you out taking pictures, and that's the most important thing.
Hope my ramblings help.