In case you don't know what minecraft is, you should go play the free version. It's lego graphics (literally), and addicting as hell. www.minecraft.net.
The sickest update is that you can create a portal to the nether world :O it's really awesome. Mine 14 obsidian stone (put water on lava, then mine. You're gonna need a diamond pick and it takes a long time) and place them 4x5 length/height with space in between. Use a firestarter in the middle and go explore.
I think I read that 10 steps in the nether world is 100 steps in the real world. So to travel great lenghts, use a portal. Walk in it. Travel a long distance and put up another portal.
Minecraft rocks ^^