Muni Alerts You can't get by in San Francisco without learning all the weird ins and outs of the Muni system. I like this app because it gives you transit arrival times (because you can't rely on those times the bus shelter gives you) and alerts.

SF Weather Why hasn't anyone done this before? A weather app that recognizes that at any one time, there are dozens of different "microclimates" all over San Francisco. Especially useful is the fact that you can look up conditions and forecasts by neighborhood, so you can figure out how many layers to wear to your protest at Civic Center or if there's going to be any sun at all in the Sunset.

Latest Quakes Armistead Maupin once wrote that a telltale sign you're a San Franciscan is that you don't say "an earthquake"; you say "the earthquake." Maybe this app will help you see The Big One coming!

California Beaches and Surf Seems to be the only West Coast-specific guide to beach conditions, so it's definitely filling a gap for all those California surfers. It doesn't just provide you with water temperatures and wave heights, either; you can even look up surf bacterial levels. A good app to have on you when you need to know if it'll be warm enough to surf at Ocean Beach or if you'll have lug your board down to Half Moon Bay for a day trip instead.

Yelp Like a lot of popular web sites, Yelp got its start in San Francisco, and you can tell: you can find almost every business in the city there. And San Franciscans are serious about their Yelp reviews, so you can actually get a lot of information here about how clean a tattoo parlor is or which restaurants make the best pho.

Craigslist Craigslist is another Bay Area brainstorm, and you can't do without it in San Francisco. Everything you want in the city is on Craigslist. Everything. Eventually your entire apartment contains nothing but Craigslist decor.