Cool Stuff

Build your own amusement part ride in your back yard. Could quite possibly be lethal if executed poorly.
The DIY Human Slingshot.

and of course the user interface of the future in

reactable: visual, interactive synth.
You need to watch some of the videos here to get the full effect of this interface.
For things like word processing, this would apparently suck, but for real-time input like when creating music, this is incredible.

My fingers are cold, this is all the text you're getting...