So these days, I'm now hooked on YELP to find reviews on all the great places in SF. And I'm not just a fan because my friend Nish is their marketing guru! It really is useful. You can read up on people's reviews of various restaurants and things to do, or better yet, send out a Yelp with a question (i.e., "anyone know a great tatoo artist?" or "where's a great place for drinks after work in Po Hill?" or "anyone know of a good hotel in Belize?") and you'll get all sorts of great feedback.
Their tagline is "real people, real review" so people are encouraged to post their photo and a bit of background on themselves too. It's sort of like a friendster meets craigs list meets city search meets match meets daily candy, and then some. Definitely check it out.