Laptop Mag's running a roundup of "the best DSLRs under $800," but all of them actually go for around $500 (w/ lens), Sony's A100 excepted, which is just under $600. Of the group—Canon Digital Rebel XT, Nikon D40, Pentax K100D and Sony Alpha A100—they ultimately side with the D40, but truth be told, there isn't a world of difference between them all. They're all great cameras for the money, really—it comes down to personal preference.
Another note: If you're looking to spend all the way up to $800, the XT and D40's bigger brothers, the XTi and D40x, are both available with a lens for under $700 from Amazon, and Newegg's throwing in a free 1GB CF card and 60GB external hard drive with the XTi. You can't go wrong either way. [Laptop Mag]