Well I'm a Nikon shooter but were I to start today, I think I'd chose Cannon. It seem's that Cannon sets the standard in digital SLR's. I have Nikon because I always have.
I would encourage you to concider only Nikon or Cannon and stay mid range price wise. The Rebel and the Nikon D50 are entry level DSLR's but work very well. Problem is that for a couple hundred bucks more you get a lot more camera. I shoot a D70 and fooled with a Cannon D20 a little. Both are great cameras and the biggest difference will be which one you like to use. I'd avoid the Olympis. They have been around for years and just recently made an entrance to digital SLR's. They are expensive, lenses are expensive and after market lenses may be limited.
Pentax D-ist is supposed to be a good camera but not many pros using it. Don't know why for sure, Pentax has always made good cameras. I have a Pentax 645NII filn camera. You'd have to kill me to get it.
Little edit here. You really should have a photo quality printer also. HP, Cannon and Epson are all excellent. But HP print's will spot and/or run if hit by water. My Epson , Epson 300, and the Cannon's won't do that. I also have an Epson 66 that works well and was cheap! Also an Epson Picturemate for 4x6's, very nice. I had the HP 4x6 printer but got rid of it when I found the ink ran if wet! Both the Epson Picturemate and the HP 375 (4x6 printer) will work on optional batteys. Speaking of batterys, get an extra for the camera and an extra card.
Let me say, look at the Cannons and Nikons that you can afford and chose the one that is easiest for you to use and feels good handling. Don't be overcome by those special programs, most, the vast majority you'll never use. One program I like on my D70 is the "commander" mode. with the right flash, I can set it off with my camera, wirelessly and remote.
For lenses, you should probally have a wide angle that comes with the camera and two telephoto's. I gave my 28-200 to my neice and wish I still had it. It was a Sigma but Tameron and Tokina also make excellent lenses in that range. I also have a 150-500 Sigma that I couldn't do with out. It comes out to about 240 -700 on a digital. It's optimised for 35mm as most are. They may make it in digital optimised now. Digitat optimized lenses will be note with a "D". By the way, if you stop at a 200mm lense, you'll come away wanting for longer shots at animals in the wild.
The longer lense, 150-500 or Tamrons 200-400 or Tokinas 80-400 all really should be shot off a tripod. If your feeling rich, Cannon and Nikon both make lenses with "vibration reduction" built in, very expensive tho, well over $1000.
I'd stick with Sigma, Tameron and Tokina lenses over the Cannon and Nikon lenses unless you a pro, maybe even then. You'll likely not be able to tell the difference in the finished photo's.
One thing not to be taken in by is the mega pixel race. Anything over 6 MP and the difference is just not that obvious to the average guy. I've blown up many photo's to 8 1/2 x 11 and they look fine. Photo's bigger than that, I shoot on film, med format film. Until you get up around 10 or 12 MP, you won't gain much. Then at 10 or 12 MP, the cost of the camera goes up, way up!
Lots of choices to make, but thats what I was looking for. Hopefully I will come away with something I can enjoy for years to come.