There are a few of groups working on Bitcoin and Minecraft integration. This is a place for the collective information to be compiled.
- BitVegas was the first casino built 100% into Minecraft. You can play with real Bitcoins that you can deposit and withdraw, or play with "play" bitcoins that can be refilled when you run out but cant be withdrawn. Features Roulette, Blackjack, Minefield and Pig Races. Texas Hold'em poker is also currently available to play in beta.
- http://www.spendlitecoins.com/ A Minecraft SMP server which featured a litecoin backed economy.
- http://dev.bukkit.org/server-mods/satoshis/ - Satoshis was a public Minecraft economy plugin in which the in-game value would be backed by the Bitcoin. This allowed people to deposit and withdraw Bitcoin into the game, and trade that value around.