An open source project to build your own off-camera flash device - OpenFlash
OpenFlash is a complete DIY solution to building your own flash device. In the repository you will find the diagrams to bake the required PCBs, component list and software to implement the functionality of a external flash device. In its current setup flashes are triggered by light and actuated by three bright colour LEDs.
This is a project of IDStudiolab - http://studiolab.ide.tudelft.nl/openflash Delft University of Technology 2013