Yelp San Francisco Office

Yelp is a local directory service with social networking and user reviews. Essentially, the site is a user driven review website that aims to help its users discover quality local businesses. The site had more than 71 million monthly unique visitors as of January 2012.
Their office not only boasts amazing views, but also a games room, cafeteria, theater, iPad keg-orator, stuffed pony, dogs, and of course a Rock Band set up!