Cory Doctrow has written a book, Makers, in which he tells a story of hackers that enjoy building new things out of trash. He has made the book available for free on his website.
Videos of each of the following are embedded after the break.
Todd Harrison carved a pumpkin like many of us, but unlike many of us he filled his with some electronics, including some lights, a big red button, and a car horn. It would be obvious enough for the horn to go off immediately when someone presses the button, but Todd made it light up the eyes, wait a moment, and then honk the horn. I want one! A video and writeup is available on his website.
Blogger Macaba created a balancing scooter that functions much like a Segway. I have been intrigued by these since I rode one, and once I get some money I very well may make one of my own.
The original source is here, but I cannot seem to find the original source’s video; this YouTube link will do. The video shows a speaking piano–that is, a mechanically-controlled piano with a computer playing the correct frequencies so that it plays back the words originally recorded into the computer. This has to be one of the coolest videos I’ve seen, and it is definitely worth watching. As a side note, I think the YouTube video I linked seems a bit spammy, but the presence of a translation makes it worth bearing.
And last but not least, three guys from Poland got together and created another of the coolest videos I’ve seen. They made a glass tabletop on which they placed bottle caps; each bottle cap represents a sound. A webcam underneath the table connects to a PC, and the PC does some image processing to find the bottle caps and play back the track, left-to-right repeatedly. It makes a lot more sense if you watch the video. A full writeup is available in Polish on their website (Polish) (Google Translation).