Not sure if anybody else other than myself worldbuilds. If you don't know what worldbuilding is, good for you, you probably have a great social life. If you for some reason would like to know (you don't, it consumes you), there's a subreddit for it at /r/worldbuilding as well as a Wikipedia page for it right
here.
Worldbuilding is basically designing a planet and then giving it a story. You can go as in-depth as you'd like (planning climates, ecology, tectonic plates, governments, etc.) or just draw a map and tell a tale. Some people start a world when they're eight years old and forget about it the next day, but some people in the subreddit have had worlds going on in their heads for a decade or two, which takes a lot more time but can get fun I guess.
I've built two worlds so far. One is based of an old Dwarf Fortress world I had and is basically my excuse for pitting heroes against monsters for a few hundred simulated years. The other is a sci-fi world with animals and governments based on all the old stuff I've made in Spore. Fun stuff.