You may have seen this little beauty floating through the interwebs. It's an Altoids Tin-based COSMAC Elf, built around the classic RCA COSMAC 1802 microprocessor. It's the prototype to a kit that Lee Hart has been developing. P. Todd Decker (Overland Park, KS) sent us a link to this video of his build of the kit prototype. He writes:

I have completed a build of Lee Hart's "COSMAC Elf Membership Card." The idea behind Lee's design was to create an interesting kit to introduce new people to the classic RCA COSMAC 1802 historic microprocessor. This processor has a long, interesting history and is even still used, due to its unique properties when it comes to power and durability. It was the basis for the famous "Elf" home-built computers from the late 1970s. It still has a strong following. Lee's twist on the old reliable was to rework it into an Arduino-style platform that—best of all for makers—fits into an Altoids can. His design doesn't require any surface-mount or complicated build techniques. Herb Johnston has done an excellent job of documenting Lee's efforts to create this kit (see link below).

Lee Hart's 1802 "Membership Card"

A wireless-enabled Arduino-based water valve controlled, neatly packed inside of a mint tin.

Minty Water Valve Controller

Marco Jetti's intervalometer triggers a still camera's shutter at regular intervals (hence the name) using a 555 timer. The movie is made up of 985 photos shot 10 seconds apart. Schematics on Marco's Flickr page.

Instructables user richfiddler11 writes:

My car stereo has only one 'Aux' input, but I have several gadgets that I like to hear on a trip without swapping cables: MP3 Player, talking GPS, Blackberry, XM player, Kindle, etc.

I couldn't find a commercial solution, so I came up with this little passive audio mixer that takes 1/8" headphone outputs from up to four devices and safely mixes the signals into one line that can feed a car stereo Aux input, powered speaker or any other amplifier that can take 1/8" stereo output.