My dad sent me this awesome article from the NYTIMES about how commuters in San Francisco are using their smartphones to "check in" at billboards using Foursquare and in-so-doing, help some endangered wildlife keep from becoming extinct. What a flippen cool way to use social media for good, no? That said, Foursquare is growing in SA. I use it every day. If, however, you have no idea what I'm talking about, check out their site and start using it today. It's a super rad way to get to know your city and let people know where you are. Who knows, one day you may use it for the benefit of mankind like they are in SF.