Found this today, it looks pretty good.
I know lots of people are into Minecraft, and maybe you would want to switch servers but not lose your items...Well, using craftcoin (CRC) you can! At least in some of the supported servers.
It's a cryptocurrency which should equate the value of 1 diamond roughly, which you can use to trade for items, or even other coins like Bitcoin and then USD if that suits your fancy.
This is the pool I'm using: http://crc.cryptocoinmine.com/
I think it's a great idea, and it should work fine after they develop the java wallet in-game.
Right now, the wallet is a c++ program, based on Bitcoin-qt client, and to get money in game you have to send it to the server's wallet who then assigns an internal wallet for your character, using the special plugins designed for this.
Few cryptocurrencies have a backing such as this, CRC actually has a practical application so in that regard it's quite revolutionary.
Have fun mining it, or mining diamonds to get it!