Keep track of your mouse clicks with the Mouse Odometer.
Face it, you know you work on your computer too much - but how much? Mouse Odometer is a mouse tracking program. It tells you how far your mouse goes, how many keys you've pressed, and how many mouse clicks you've had for every application you use. Mouse Odometer has tons of other special features, and best of all - it's FREE
This looks like it might be fun. By the way, the source code is also available -- which means that it's probably not a spyware app.