Well I should really create an "intangible" category here! If your are into neurofeedback, EEG biofeedback, brainwave interaction or brainwave controller, you should have a glance at the openEEG project:

The OpenEEG project is about making plans and software for do-it-yourself EEG devices available for free (as in GPL). It is aimed toward amateurs who would like to experiment with EEG. However, if you are a pro in any of the fields of electronics, neurofeedback, software development etc., you are of course welcome to join the mailing-list and share your wisdom.

Right now, this site is mostly about the hardware; schematics, part lists, building instructions etc. However, a few members have developed some useful software which is hosted on their own websites. You can find these through the software pages.

Why do I blog this I am wondering whether there will be a post-dorkbot trend: instead of "people doing strange things with electricity", the motto would be "people doing stange things with brain waves". Here are the already existing apps. I am looking forward to see crazy applications with tangible feedback created/controlled by intangible brain waves!