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/

Edit details in individual minecraft worlds, import/export schematics, delete and repopulate chunks, and run filters like changing biomes. Make sure to use the development version for recent versions of Minecraft. You need access to your world file (personal server or single player) in order to use this.

Binvox

Hard | Open Source Script | http://www.patrickmin.com/minecraft/

Import 3D models into Minecraft. Great for building space ships or statues, can export to a schematic file for use in MCEdit.

World Painter

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

Paint and modify entire Minecraft worlds using powerful tools and filters. Large scale editing. You will need access to your world file (personal server or single player) to modify existing worlds.

AMIDST

Easy | Open Source Software | http://www.minecraftforum.net/topic/626786-v34-amidst-strongholds-village-biome-etc-finder-13w39b/

See what kind of world layout a seed will generate - including biomes and features like villages/temples. You need access to your world file or world seed to use this tool.

Schematic 2 Blueprint

??? | Open Source Attribution | http://klaue.net16.net/programme/ownprogs/java/schematic2blueprint.en.php

Just discovered this, evaluating now. A tool to convert .schematic files to blue prints for building on survival and closed servers.