Just now I read an interesting lifehacker post that talks about IOGraph, an application that tracks your mouse movements (not in a bad way) and displays a picture of where you frequently click your mouse. It doesn't show what websites/documents you clicked your mouse in, just the position of the mouse click. Here's a demonstration of the application. It spent 32 minutes tracking my mouse movements. My dock is on the bottom, and I find it interesting that I don't use it that often (autohide is on).
The application is free and the lifehacker post can be found here. The black circles mean that your mouse stopped there.
Here's another one after roughly 2 hours of usage