I'm stuck between buying SLR cameras?

I'm about to buy an SLR camera, but I'm not sure which one is between, the Nikon D3100 or Sony a33
or if there's a better choice let me know.
My budget is $1000

Added (1). I decided that the Sony A33 was a waste, so i kept looking and found that the rebel t1i was pretty good. So now its between the rebel t1i and Nikon D3100
and if it's really worth it, what about the rebel t2i

Canon EOS Rebel T2i is a great camera, I'd consider it.
But, if it is between those two, the Nikon.

Buy the Nikon. They have many more lenses available for when you want to upgrade.

On your short list, yes the Nikon. But I'd also ask you to consider the Canon t1i (which I own) and the t2i - both new and excellent cameras.

I wouldn't touch that sony with a bargepole! An electronic viewfinder on a DSLR?

At the moment there's some very good entry level model DSLR on the market. One of the main distinctions is high iso performace, the ability to produce clean, crisp images in low light without flash.

Pentax K-x: Winner of a few awards. Only DSLR that runs on AA batteries which means you need to exercise some discipline in charging and handling them. Can use simple Alkaline batteries in emergencies. Won a few awards, got good reviews. Pentax' lens lineup is better than that of olympus.

Sony A33/A55: Looks very impressive on paper, especially with it's 10fps. Perhaps the best video autofocus on the market today. The electronic viewfinder (yes, a DSLR with an electronic viewfinder!) is not to everyone's liking. It does delay slightly and it's a significant battery drain. With a mere 330 photos per battery charge it's by far the weakest in that respect.

Canon 1000d/Rebel XS
An entry level model dating back to 2008. Basically a 400d/Rebel Xti with some features removed in an attempt to compete with the baby nikons. Long overdue for replacement. Good lens lineup.

Canon 550d/Rebel T2i
Canon's entry level camera. Quite a capable camera but it continues the long Rebel tradition of putting a very good sensor in a plasticky body with some rather poor controls. Still offers the best video of any entry level DSLR and enough megapixels to impress all of your gullible friends

Canon 500d/Rebel T1i
If you're not interested in video you can buy this instead of the 550/T2i and save yourself a few bucks

Nikon D3000
Critized by many for reusing the old D40x/D60 sensor which means mediocre high iso performance. Despite that it's still a lot of camera on other points. Controls and handling are generally perceived to be better than Canon's xxxd/Rebel series. Only takes nikon AF-S, Sigma HSM or Tamron BiM lenses for autofocus.

Nikon D3100
Fixes everything that was wrong with the D3000 and then some! Most impressive entry level DSLR released this year. Truely impressive high iso performance. Comes extremely close to beating the 550d/Rebel T2i on video but it's more affordable. Nice built-in guide mode to help handhold the beginner who doesn't want to read the manual. Only takes nikon AF-S, Sigma HSM or Tamron BiM lenses for autofocus.

What else to buy?
Unless you have any real specific purposes in mind I'd advice you to start with a single lens and gain some experience before buying more. Do buy a memory card, a lens pen or microfiber cloth, a rocket blower and some sort of protective bag.

Sony A55 or A580. Both have the same sensor as the Nikon D7000 and the A55 is flying off the shelves despite what you'll read here from biased Nikon and Canon users.

There are plenty of lenses for them, Sony bought Minolta, so every Minolta AF lens works on them, that's 25 years worth. In fact there are more lenses that will auto-focus on the Sony than there are that will auto-focus on the Nikon D3100, which does not have an auto-focus motor. That's something the Nikon boys forget to mention…

Buy Nikon if you must, you probably will not be disappointed. Canon is my preference. Buy Sony? No, never,
not because of the camera but Sony does not stand behind what they sell as well as Canon (Nikon? I don't really know, but no bad reports). Even when Sony was the Minolta brand ( although a good camera) could not measure up to Canon or Nikon.

Good Luck

P.S. I just noticed that another contributor listed the Pentax Kx, I would have to second that nomination as I just purchased the Pentax Kx and love it. The uncluttered viewfinder attracted me and the "feel" of the camera!