Welcome to the Full Solar System 1.3 by Jason Took the Aliens! This adds the rest of the planets, and some other things. Here's a list:
Apophis
Ceres
Saturn, Titan, Rhea, Enceladus, Mimas
Uranus, Ariel, Umbriel
Neptune, Triton, Proteus
Pluto, Charon
Haumea, Namaka, Hi'iaka
Sedna
1.3, released...