(Project Icarus) Taking pictures of Earth from near-space for under $150. How-to guide available.
(Scanimations) Like the book "Gallop," but click-and-drag DIY in an HTML5 canvas. Kits available.
(MoiréMe) Spatial analog of FM radio. More mathematical than Scanimations. Kits available.
(Laser Wiretap) Low-budget laser wiretap. Use a laser beam to detect and listen to music behind a distant glass window. Coming soon.
(Lenslet Arrays) DIY Glassesless 3D display. Great for teaching/demonstrating how lenticular arrays work. Coming soon.
(GrIn Blocks) Bouncy lasers. Coming soon.
(Other) List of other projects on the to-do list. (Legoify, Displayblocks from Media Lab, Land's color experiment, LCD screen w/o polarizer, Craftwork)