Animal Jam
Animal Jam is a virtual world made by WildWorks and the National Geographic Society. Many of the players in Animal Jam are children and teenagers. According to the WildWorks website, the game has about 160 million players. Animal Jam is one of the fastest growing children's games in the world.  The game is free to play, but to be able to receive all the things Animal Jam has to offer, a membership needs to be purchased online or through a store-purchased gift card.