On a common note, if your budget is tight, and unless there is a particular characteristic or performance level you require from a particular model, it is commonly an excellent idea to save money on the body and spend it on a excellent lens.
For the excellent Nikon value, the D7000 sends the excellent bang for an admittedly not-inconsiderable quantity of bucks. If you are willing to shell out a little, though, you receive best picture quality, D300s-level function for entire but continuous shooting, and Nikon's excellent dSLR design now. It does not have the construct quality of the D300s, but it is fairly well built nonetheless.
If you require a pro-level camera but can not afford the D3, and do not require the lens compatibility or wide-angle flexibility of a complete-frame model, the D300s offers a some advantages over the lower-end models. It is excellent constructed, with a dust-sealed body and furnished a more sophisticated 51-point AF system. Its burst function outpaces the D7000 as well. Nikon has discontinued the still-excellent D300 instead than only dropping the cost as I had hoped, but if you do not required the video support and can search it for less than the D300s, it is a worthwhile alternatives.
If you require a more rugged body, excellent low-light latitude, or actual wide-angle focal lengths under 20mm or so, then it is time to step up to the D700. It sends a couple stops of exposure above the D300s--up to ISO 12,800 is operational on occasion--and because it is complete-frame, it deficiencies the 1.5x magnification element that narrows wide-angle lenses.