I have a Nikon D80 and a Nikon 105 f/2.8 prime lens. An outstanding combo. If you want to do all your own settings, and control your photo input, this is a fanastic lens. Sigma makes good lenses, but I prefer keeping Nikon to Nikon and found mine on eBay for a lot less than $500. Whatever you get, try eBay listings. Lenses are a perosnal choice, so get the type you want, but shop a bit. If you find an older Nikon lens, be sure it will adapt to your D80. Older Nikons need to be Ai or AI-s. Also, check Ken Rockwell, the Nikon "Guru" -
http://www.kenrockwell.com/index.htm/105mm f/2.8 -- Good luck and good shooting -- Johnniejack