You might also consider Pentax. One of the threads to which phanoohish linked includes my thoughts - and some excellent posts from pop and others - as I went through the same process, albeit with a slightly higher budget (which I've since blown, of course!).
You could pick up a used K100D (in the $300s somewhere) and have some cash left over for a fast 50mm lens, and have some cash left over for maybe a used Sigma 17-70 f2.8-4.0 for some walkaround flexibility and good image quality without breaking the bank. Or if you really want to stretch your dollar, Pentax has very good (though not perfect) backwards compatibility between their dSLRs and old film lenses, both Pentax and off-brand, and at reasonable prices, to boot. Most of the older lenses are manual focus, but I find myself preferring manual focus more and more these days. IMO, the big advantages Pentax brings to the table: <1> in-camera Shake Reduction (v. the far more expensive Nikon in-lens Vibration Reduction, or Canon in-lens Image Stabilization), <2> loads of legacy glass with very good backwards compatibility at low-medium prices. And you get the benefits of SR in every lens you use, new or old, inexpensive or big bucks.
Lots of info and a pleasant user forum, a la TS:
http://www.pentaxforums.comI
strongly recommend finding a local shop that carries Canon, Nikon, and Pentax. Try the different models in your hands, see how they feel, try the hard-button and software functions to get a sense for how they're used in the field. I didn't like the ergos and hard-button and software functions of the Canon. I was familiar with, and liked, the Nikon ergos and functions. But over both I preferred the Pentax ergos and hard-button and software functions.
Lots of great options, I suspect you wouldn't be disappointed with any camera / lens combo in your price range. FWIW, my biggest challenges continue to have nothing to do with the camera: developing my artistic eye (looooong wya to go), and learning how to use the tool effectively and efficiently (getting there, though slowly).