IMHO a 50mm lens is still very useful on a crop-sensor DSLR but it's not really a "standard" lens more like a short tele. The first lens I messed with on a film camera was an 50mm but for crop sensor I have a 28mm lens as my "standard." I also have a 55mm though. h:

In your price range I'd look at any of the following bodies, can explain in more detail if you want.

Canon XSi, 30D
Nikon D70
Pentax K100D, K100D Super, K110D, K200D, K10D

I'm a little biased towards Pentax (I have a K-x) because I nerd out on the ability to buy a $15 manual focus lens on ebay and use it with semi-automatic exposure and image stabilization. h: