Just a bit of info regarding custom VJ controllers.

Here you can find software for converting gamepad signal to midi:

OSX: junXion  (Uh…lame, this is pay to play. Let me know if you know of an open source option.)

Windows*: Rejoice

*for windows you will need MIDI Yoke

Start off with something like a wireless PS3 controller and see how things go for you. Wireless PS3 Guitar Hero guitars are a lot of fun on the dance floor and draw a lot of attention. Once you get the hang of just using a standard controller in it’s original configuration, get out the screw driver, soldering iron, some wire, and buttons. Create whatever shaped controller you want by just soldering directly to the pads on the controllers PCB. Make sure to scratch the pads a little bit before soldering to give a nice surface to work with, but not too hard, the metal is rather thin.

Don’t forget, if you don’t want to deal with the software side and gamepad/midi configurations, just rip apart a usb keyboard and rewire directly to the PCB.

Feel free to send me emails with any questions you have (email address in the header).