There are plenty of things to do in San Francisco that don't cost money and are awesome. Here are some:

• Every Wednesday, free trivia hosted by stand up comedians followed by a live band, 8pm, at Tupelohttp://tupelosf.com/#bookings
• On the first Tuesday of each month, you can visit the San Francisco Museum of Modern Art, Asian Art Museum, M.H. de Young Museum, Legion Of Honor, or Conservatory Of Flowers .
• On the last Friday of each month, you can bike along with Critical Mass.
• First Wednesdays of the month are free at the Exploratorium.
• The Japanese Tea Garden in Golden Gate Park has free admission before 10:00 am on Monday, Wednesday, and Friday.
• Sit in on the Ninth Circuit Court of Appeals or California Supreme Court oral arguments. For reals, it may be more fun than you think.
• On the last Saturday of each month, head over to the Really Really Free Market in Dolores Park.
• There are bonfires on Ocean Beach every Saturday night.
• Go to one of several public libraries!
• Take an introductory meditation course at the Kadampa Buddhist Temple on Tuesday nights. If Tuesday night isn't good for you, take in an hour of yoga and thirty minutes of meditation on Friday night at the San Francisco Buddhist Center. (Both are donation-only. No one is turned away due to lack of funds!)
• If you're into archery and have equipment, you can shoot in Golden Gate Park's range.
• SF0 ("SF Zero") hosts a self-described "collaborative production game" that resembles a scavenger hunt.
• There's a Flickr pool called Guess Where SF (similar to davis's Mystery Picture!) that you can contribute to or make guesses on.
• Go to the Independent on Monday nights for a free flick.
• Free outdoor movies are often screened in the summer. Thrillist has a list.
• A good source of free (to cheap) things to do can be found at FuncheapSF
• Free wifi! Available in many locations, including city-provided free wifi spots listed at SFGOV, and Parks and Recreation provided spots.

There are probably also plenty of places to get some free food. Here are some:

• Eat the free cheese and olive samples at Rainbow Grocery and Bi-Rite, but don't be, umm, overenthusiastic.
• Trader Joe's has free coffee and often food samples, as well.
• Do the Freegan thing and go dumpster diving!
• Art openings often have snacks. Check out the Guardian, Indybay and other local media to find out about that.
• The Ferry Plaza Farmers Market always has a plentiful amount of free fruit samples.