There are plenty of Nikon D80s & D200s second hand, you have just missed Derek's, but a lot of folks have upgraded to D300. D80 if you prefer small body with most of the D200 features, D200 if you like a good lump of metal in your hand and need some of the slick bits (see Michael Hogan's 2nd body thread).

The D80 was offered with a 18-135 kit lens for next to nothing, but it is very good indeed and worth including if in an offer.

Only qualification and reason for going for later generation new is that built in cleaning is included in the latest models Clive flags up