Pinterest is a kind of visual bulletin--or inspiration--board. Users, who currently must request an invitation to join Pinterest, create boards with categories like "Books I Love" or "Beautiful Places" or "Products That Save Me Time." Users can then link images from websites (using a Pinterest browser bookmark) or upload images from their computers and "pin" the images to the boards. As with Twitter, users can follow other users, and Pinterest images can be repinned and shared. Pinterest is rapidly gaining users and mindshare, and it is becoming a huge driver of referral traffic.