I know you're bummed because it's summer now and there's not much snow left in the Sierra to crush, but there's a (somewhat, relatively) new sport in town: Freebording. You can carve and slice and fall on your ass just like you're snowboarding, but do it while bombing down Dolores on your way to beers and hot cocoa in the park. It's like snowboarding, but in traffic. They've even got one helluva video showing how it's done (and the legal implications of doing it):
I suppose you should go out and buy one, as I guess this makes bicyclists the two plankers of the streets. Plus, they're made right here in San Francisco.