Oskar Stalberg’s online game/toy “Polygonal Planet Project” runs in the browser and lets you design your own wee planet. You can raise and lower land, ice, forests and cities in a way similar to Amiga classic Populous, and watch the 3D globe rotate.
It’s pretty hard on the old CPU—my little Macbook struggled with any world larger than the smallest option—but lights a strange little fire in the creative part of my mind. He also made one for 3D houses, which is just as much fun!
Update: “Or download a faster version for your desktop at:
http://oskarstalberg.com/game/planet/planet.rar”