Here we go
Well, all depends on what you really want to do, prosumer photography? here are a few choices:
Nikon D40X, 10Mp, lots of lenses to choose from.
Canon 500D, 15Mp, Like Nikon, lots os lenses to choose from
Sony Alpha 350 (now 380), these thing takes lenses from minolta, Konica and Sony.
Lenses is allways the problem to choose from, they will live longer years (ALOT) than your camera (whatever brand it is), so choosing a good lens is allways the place to put the bucks in, the camera itself... eh.. now is this, tommorow will be another one, but keep in mind, like Johannicus stated and trully, they are not interchangable beetwen brands with one exception... minolta/sony have adapters for other brands, of course adapters may not give the best results than a native bayonett, even more now with "intelligent" lenses, diaphragam motors and inbuilt steady shot.
Sony on lenses take the best bet, they can mount Carlz Zeis Vario Sonar lenses, believe me, my 350 looks another thing with one on, I have the lenses that came in the 350k package (cheap lenses) and a Zeiss is quite different (ALOT), however they cost like hell on earth, a simple 35-110mm goes around 1700eur (~1500£).
I'm into Sony for digital, some examples can be seen on my gallery.
Now it's just a matter of choice. Keep allways in mind, the camera body is "disposable" the lens aren't.