Science in the Bay Area
Exploratorium in San Francisco
California Academy of Science in San Francisco
California Academy of Science has a natural history museum, aquarium, indoor rainforest, and planetarium. They also have great events periodically like sleepovers.
Tech Museum of Innovation in San Jose
The Tech Museum of Innovation in San Jose has a number of exhibits including: Cyber Detectives, Social Robots, Body Worlds Decoded, Innovations in Health care, and a few others. Well worth the drive to the south bay!
Lawrence Hall of Science in Berkeley
Lawrence Hall of Science is in the Berkley Hills and has a number of exhibits and a planetarium. They also have an excellent store with books, activities, and science-related games.
Chabot Space & Science Center in Oakland
Chabot Space & Science Center is located in the Oakland hills. There are a number of hands-on interactive exhibits, a planetarium, and events.
They also have star-gazing on weekends. Check site for dates.