Exposureplot is a nice little free utility that will show you a summary of the focal lengths most used with your shooting. That comes in handy when you start thinking about a new lens and wonder if you want to go for a telephoto or a wide angle. If you are thinking about primes, you can see where your zooms get the most work too. As a bonus it will also plot ISO, shutter speeds and f-stops. Here is an example of the output from one folder of mine.
There are several other viewing and analysis options that will be worth your while to try.