A Multimedia tour of the universe Information about the planets, their satellites, comets, spacecraft and missions. This page from NASA includes information about each planet in our solar system as well as many NASA expeditions. Lots of pictures, but limited information. This site is not as great as Nine planets. This site is packed with information.
Information is in English, Spanish, and Portuguese.
These questions and more are answered at this site. A very visually attractive site. There's a whole universe beyond our solar system, see hundreds of images of it here. Includes a good introduction to Nebulae. This site is nicely organized and explains the basic concepts of biology very well.