Groupon is offering a Bay Quackers deal today for $17 a ticket (normally $35). Tours leave from Fisherman's Wharf. (Read about some cheap family-friendly Fisherman's Wharf attractions here). The tour lasts 80 minutes.
Small print - you can buy four tickets max - they expire in a year.
Get the Bay Quackers deal here - today only.
Savvy Source is offering a great deal on admission to Habitot in Berkeley. For $35, get 5 passes (which admit three people each) to this acclaimed hands-on kids' museum. You can also sign up on their site to get the deals directly in your mailbox. 5% of all purchase prices go to the preschool of your choice.