Here looks like a good place.
http://brmlab.cz/project/brain_hacking/tdcs
I'm going to be experimenting with them at the london hackspace so anyone from london is interested, give me a shout,
That ones actually a bit dangerous. The current regulator is rated to go that low, so it's going to be unreliable. In this instance unreliable means brain lesions.
Article here;
http://www.ox.ac.uk/media/science_blog/brainboosting.html
The article goes on to discuss the ethics of the technique.