PiBakery is a program that allows super-easy presetup of Raspberry Pi SD cards. Customisation is done using a Scratch-style interface, where each block represents a script to run on startup.
Anyone can create and add new blocks to PiBakery, meaning that if there's a setup task you always do to a new Raspbian install, or if you have some software you'd like everyone to be able to easily add to their Pi, you can create a block, and people can just drag that block into their setup script to run your code! Anyone can create a block, and once it's been added to this GitHub repo, everyone running PiBakery will automatically get the newly added block.
Creating a PiBakery block
The instructions for creating and submitting a block to PiBakery have moved to the PiBakery website