Edit: just noticed in the OP that you don't care for flash stuff but I'm keeping this here anyway
I went from D50 to D90 and couldn't be happier. It has a built in AF motor so it can take better advantage of the older generation Nikkor prime lenses compared to the "entry level" D40/60/3xxx/5xxx, plus it has some other flash related tricks like High Speed flash sync capabilities and it's pop up flash can be used in Commander Mode for the Nikon CLS off-camera flash system.
It's also pretty comfy to shoot with once it's bolted to the MB-D80 battery grip. I don't care for video so I'm sure some motion shooters will chime in with how dated the D90's video mode is, but you can't really go wrong in the bang-for-buck department.
This deal on KEH.com aint too shabby either.