Mojang have teamed up with PC Gamer to release a Minecraft demo for the masses. It’s a good deal too, the whole game is available, but you can only edit the world for 90 minutes, at which point it locks down and becomes uneditable. If you like the game, but want to try another world, just make another world – the number of worlds you can make are endless!
Surviving Minecraft, Minecraft Adventures! 