Nikon's latest D40-descended entry camera is the $450 Nikon D3000. The camera on its spec sheet is decided low-spec compared to what else Nikon offers but on-par with Canon's 1000D and Sony's A230. Its 12-bit 10MP sensor has dust cleaning functionality, and calibrated ISO to 1600 (pushed to 3200) put it on par with mid-range or entry-level cameras from a couple years ago. The D3000 has the latest version of Nikon's Expeed imaging processor, but if the camera feels limiting deals can be had on an old or used D200 if you're interested in Nikon; or Canon EOS 450D (Rebel) and Canon EOS 40D which are similar spec with newer imaging system than the D200.
Where the D3000 might be beneficial is with its on-board guides, designed to help new users. If you do not think this is useful, stay out of the entry range.