Depends on what you're into.
Haight-Ashbury is good for travellers, and there's free breakfast at Larkin St. (in Haight, by Buena Vista Park)
Golden Gate park is awesome, more places to chill than you can think of.
Take the BART to Berkely, hit up Telegraph. If you are into punk music, go to "Gilman St." Cool venue, a lot of free/cheap shows.
North by hitching, take the bus to the Golden Gate bridge, walk it, first onramp.
Richmond for freight, near oakland