If you are visiting San Diego, take a break from the zoo, and go see the San Diego Air & Space Museum, also in Balboa Park.  It is California's official air & space museum, and is affiliated with the Smithsonian Institution.  It is a great way to spend some time.  Four general admission passes.

www.sandiegoairandspace.org

Also, for those planning a trip to San Diego, check out:

Hornblower Cruises, the USS Midway Museum, and the Torrey Pines Paragliding items in the auction.