I got a fantastic deal on eBay on my Olympus. There's always somebody with more money than you wanting to upgrade. They guy who sold me mine probably wanted a D90 or something, so I got a bargain. Somethings I'd never buy used, and other things it doesn't really matter. A camera is definitely the latter. Plus, by saving 5 bills, you'll be able to buy a couple of lenses that you'll desperately be wanting if you buy new. Lenses ain't cheap.
Edit: cameras either come body only, which as Orcus said is no lenses, or you can buy the camera with one or two kit lenses. The kit lenses aren't great, but they're more than adequate. Figure that 1 good lens, and you'll want at least 2, will run you 3 or 4 bills. 2 kit lenses will add $150 or so to the cost of the camera.