What a deal! On the first Wednesday of every month, from 10 a.m. to 5 p.m., the usual admission fees at the Exploratorium are waived entirely. Note: Children under four get in free all the time. And as far as museums go, the Exploratorium is unusually kid-friendly, with more than 100 hands-on exhibits.
3601 Lyon St.
(415) 561-0360