Of all the ways
to spend money on camera gear - a good lens is the best place
to start. Nothing can be more of a hindrance to getting good
shots than having a low quality lens. Digital imaging is quickly
changing the rules for much of photography but the basics remain: you have to have a good lens to focus the
light accurately with as little distortion as possible. Digital
cameras are also allowing us to shoot at higher and higher
ISO values with little noise; however, it is always advantageous
to have as fast a lens as possible (large maximum aperture)
to ensure you can capture low light images when the time comes.
Also remember that a lens is a much more important investment
of your money; digital SLR bodies are essentially disposable
being obsolete in 2 to 3 years. A good lens, on the other
hand, will hopefully be used for a longer time period.
My best current lens is my Canon 17-55 f2.8, which I review here.
I have had a number of Nikon lenses for use on a Nikon FE2 - you can read more about them at my Nikon Lens Page.