I've already told you about free day at the Exploratorium, but how about free day at the San Francisco Zoo?
If you're a resident of San Francisco, you can enjoy free admission on the first Wednesday of every month. You'll need to bring proof of residency, such as a valid drivers license, ID card or utility bill. Unfortunately, if you are not a resident, you won't get in free, unlike the Exploratorium.
For more information, click HERE >>
Hours: 10am-5pm. San Francisco Zoo, 1 Zoo Road, San Francisco, CA, www.sfzoo.org