From National Geographic comes The Atlas of Moons, an interactive reference to all of the major moons in our solar system, from the Earth's own moon to the Galilean moons of Jupiter to Charon, which forms a binary system with Pluto.
For whatever reason, I wasn't fully aware that some of Jupiter's and Saturn's major moons orbited their planets so quickly — Europa takes 3.6 days to complete an orbit, Io once every 1.8 days, and Mimas speeds around Saturn every 22.6 hours.
