National Geographic’s Atlas of Moons

The Atlas of Moons (screenshot)

The Atlas of Moons is National Geographic’s interactive guide to every single moon in the solar system (except for a few moons of dwarf planets and asteroids that we know next to nothing about). The big ones get interactive globes and additional description (as do Mars’s moons Phobos and Deimos, because we have imagery for them). Note that this is an extremely resource-intensive page that will use gigabytes of RAM if you let it.