Something I'm still surprised to see in San Francisco is second-hand stuff left along the street in residential areas. Couches, chairs, dressers, VCRs, all manner of things. It's like a yard sale but without the sale. And it's not like there's a big pile of junk -- it's usually just one item all alone along the street. What's the social contract? Apparently, it's: it's okay to leave an item or two that you don't want anymore, so long as it's at least visually okay looking. Leave it on the street and forget about it. Likewise, if you see a couch or VCR along the street, it's fair game: if you want it, take it. No need to find the owner, although don't be silly: if there's a garage open right there you shouldn't just walk off with someone's bike. [Sad sign Melinda and I saw on her street: "Please return our swim suits and wetsuits. They were just drying!"]
My commute from SF now involves walking from 5th and Parnassus to Carl & Cole, a ~10 minute walk past scores of apartments and 10 blocks of this virtual second-hand store. I'm going to try recording what I see along the way. In the past it's included: an ironing board; a VCR; speakers; chest of drawers. Last night I saw a mac keyboard and miscellaneous clothes. Tonight the keyboard was still there, the clothes were gone but I saw a towel elsewhere.