The Pet Shop is home to three games based on the puffles.
Two of those games (Pufflescape and Puffle Launch) has stamps.
Puffle Roundup doesn't not have stamps, because none were created for it. It was one of the original games on Club Penguin.
Pufflescape-- Pufflescape is located next to the entrance to the Pet Shop. It has a hamster ball (Puffle Ball, in Club Penguin) for your puffle to roll around in, trying to escape the cavern. Along the way, while trying to grab the key, you can collect Puffle Os, which increase your score, and your winnings. The Rainbow Puffle cannot play this game yet.
Puffle Launch-- Puffle Launch in located right in between Pufflescape and Puffle Roundup. It has a red cannon and a red puffle inside. This game, you have to launch your puffle (Any of your puffles, or the default red puffle, Daredevil) to collect Puffle Os and to build your cannon, which you can place inside your igloo to start the game there. The Rainbow Puffle cannot play this game yet.
Puffle Roundup-- Puffle Roundup is likely one of the most easiest ways to earn coins. If you play more then one level, you can earn nearly 100 coins in two levels. Keep playing to earn more. You use your cursor to lead the puffles into the pen. Some are near the edge of the playing area. If one goes out of the playing area, it has escaped. You have 10 puffles to roundup in two minutes. All colors of puffles are in the game, except the Rainbow Puffle. You do not need your own puffles or a default puffle to play.