I once found a nice program that allows one to analyze the metadata of all your photos. It then creates 4 graphs showing a histogram of focal length, shutter speed, aperture and ISO. I think especially the focal length histogram is interesting if you thinking about lenses. An analysis of 15,500 pictures that I've shot with the D80 showed that most of the photos were taken from ultra wideangle to about 65mm. The big bar at 50mm is because of my 50mm f/1.8 lens that I use for low light photography and when I think image quality is important. Generally I like the 50mm, but I think a wider one would be better, something like a 28 or 35mm which would be a true normal lens for the D80. Of course the histogram is biased to the lenses, but it was surprising to see that even with my 18-200 I mostly stayed at a wider focal length.

The program that can create these statistics is called ExposurePlot.