We've touched upon computer numeric control (CNC) projects in the past, looking at Eberhard Rensch's impressive Pleasant Flasher small-volume manufacturing and the low-cost Piccalo robot, but sometimes you're not looking for even the hint of practicality that comes from drawing doodles on a sticky note. Thankfully, Arvid Jense and Marie Caye have the answer: an Instructable guide for an Arduino-powered CNC Spirograph which draws edible patterns on biscuits. For those who have wanted to experiment with CNC but baulked at the cost: aside from an already-owned Arduino microcontroller and a broken hi-fi stereo which could be salvaged for parts, the entire project came in at under £5. Granted, making wobbly glazing patterns on biscuits isn't the most practical of projects - but it's a great, and cheap, introduction to CNC and a project where even the failures are undeniably delicious.
For some reason brainstorming always happens late enough or lasts long enough to get you dead hungry. That's how you get an idea like making a CNC cookie Spirograph decoration machine.