I have played the excellent game of Minecraft for a week now, and am entirely hooked. I have built up a little base in what appears to be a massive map. I have read that it could be as large as Earth (wow) Is anyone crazy enough to try and explore it all.
Each map is random. So everybody's environment is different. It is a huge somewhat silly looking sandbox game. Play it in Peaceful mode, or try Survival against a host of enemies. Careful, some enemies explode.
Here's a recent overview map I created of my Minecraft I explored so far.