I decided that I would like to have a programmable temperature-based fan speed controller for a fume extractor I am building from scrap parts, and the logical thing to do seemed to be to use an Arduino Nano as modern fans use a 5 volt PWM signal to control their speed, and also report back their speed with another 5 volt signal. They are also wicked cheap if you are willing to use clones.
Long, long ago, when I first heard of Philips Ambilight, I thought it was one of the coolest silly things I'd ever heard of. Today, much later, I finally have gotten around to rolling my own Ambilight clone using an Arduino Nano and WS2812B strips. I did not have to write any code, because other people have already done it for me. Figuring out which people had done what properly took me the better part of a day, so I will now share my knowledge with you here. This should be a cross-platform (Win/Lin/Mac) solution, but I have only tested on Windows.
Faced with the desire for a GPS-navigating fixed wing drone, I came upon PatrikE's fork of MultiWii 2.4. I forked it some more, to produce a version with SD card logging. The result is multiwii-2.4-fixedwing on github.
Some little while ago, I picked up an e-Flite Apprentice, a fairly common foam "trainer" model airplane which is normally sold "ready to fly" with everything but the battery and charger. It was part of a lot of stuff that I picked up for ten dollars, and came without the radio. First I repaired it and mounted a HobbyKing HK-T6A v2 radio, but I quickly decided that it should be more than just a plane.