The distance your mouse travels when using the computer. You might be amazed at the number of miles you can rack up especially when surfing the Web. There are programs on the market that track mouse miles.
Mouse Odometer let you keep track of your mouse miles (or feet, inches, etc.) and also let you know how you fared compared to a bunch of distance landmarks. The "I Want To" button took you to all the options. (Screenshot courtesy of Introspect Software)