Etsy
The company has been profitable since 2009, thanks to the site's more than 1 million active sellers, who made $895 million on goods last year.
(Etsy's main revenue comes from charging sellers $0.20 to list a single item for four months, and then 3.5% of the value of the sale if someone buys an item.)
As you'd expect, the office space has an artsy, quirky feel, but the team also has several sustainability initiatives.