Champaign-Urbana Community Fab Lab

This isn't yet a formal tutorial, just resources for 3D modeling and printing with Minecraft:

Fab Lab Creative Server

Easy | Online Sever

Connect at fablab.no-ip.org:25567

Printcraft

Easy | Online Server | http://printcraft.org/

Create in game on an a plot, get emailed your 3D model.

Mineways

Moderate | Open Source Software | http://www.realtimerendering.com/erich/minecraft/public/mineways/

Export sections of maps, including creations and terrain of existing worlds. You need access to your world file (personal server or single player) in order to use this.

MCEdit

Hard | Open Source Software | http://www.mcedit.net/