One of my hobbies is computer science education for children. Over the past year or so, I've been developing Raspberry Jam Mod (requires Forge and Minecraft 1.8), a Minecraft mod that implements the Raspberry Pi Minecraft API and allows one to write Python code that connects with Minecraft (this isn't that original: there are two other projects that do that). I taught some Python to gifted middle- and high-schoolers in the summer using this setup.
Over the last couple of days, I decided it would be nice to make something like this available for younger kids, using Google's Blockly graphical programming environment in place of Python. It's nothing very sophisticated, but you can use 3D turtle graphics commands to draw stuff in Minecraft. If interested, install Forge for Minecraft 1.8, then Raspberry Jam Mod version 0.50 or higher, start a single-user Minecraft world, and point your browser to robotblocks.appspot.com to get the Blockly code editor in-browser. The in-browser Blockly editor should then talk to your Minecraft.
Source code for the Blockly stuff is here.