This site, provided by NASA, Space Science Institute, and National Science Foundation’s Division of Informal Science Education, features interactive activities for students to learn about space. No, this isn’t about the rich and famous. Alien Earths Online has a section on Star and Planet Formation with wonderful images and slideshows. It also include a Planet Families activity:
Try to build the perfect solar system. See how different planets react with one another, and see how some planets are important in keeping the solar system stable. Play alone, or team up with other online players!