I'm always on the look out for ways to waste time online. KLM make up for their mediocre in-flight service by providing a wonderful public service that plots where you've been in the world. Use to boast to your friends how well travelled you are!
I suppose this also helps me prioritise where I want to go next. For various reasons I spend most of my time between London and the States, but I really want to spend more time in S. America. Brazil and Argentina have to be top of my list. I wish I had the money, but even more, I wish I had the time!
Update: The map link is broken, and thus, removed.