Wikipedia (blargh) said:Minecraft is a sandbox game which allows players to build constructions out of textured cubes in a 3D world. It is currently in development by Markus Persson, aka "Notch". The gameplay is inspired by Dwarf Fortress, RollerCoaster Tycoon, Dungeon Keeper, and especially Infiniminer. The game is split into two variants, Alpha and Classic; Classic is both single- and multiplayer and includes only the building aspects of the game with unlimited blocks, and Alpha also has a single- and multiplayer mode and includes monsters and a much greater variety of crafting available, as well as requiring players to mine their own blocks. Alpha is currently the alpha release of Minecraft, and will move into beta sometime in August 2010. Minecraft was developed for about a week before its public release on May 17, 2009 on the TIGSource forums, where it gained a considerable level of popularity. It has been continually updated since then.
I'm just going to get this out of the way. I love this game. The gameplay is interesting (Even better in Alpha), the level generator is awesome, and the massive range of materials for you to use is insane!
I'm saving up so I can get this game before the Notch bumps up the price when it hits Beta. As of the moment it's $13.
Now, I think these screenshots are from Classic, but it's still worth the money.