UPDATE: the link is dead.
I'm not a fan of Minecraft. Long time ago I've spent hours in front of my 3D Construction Kit when I was a teen. But it has a great community of fans, and one of you has created a series of "hacks" decompiling the binary (Is it legal?) so you can do some things that are not covered.
The Howto is not ended, but updates coming soon.
Link: How To Hack MCPI - Dropbox (pdf)