I might start a short series of dueling flashes. It is turning out to be a very busy week so I am going to go for a repeatable series that is QUICK, but I will still try to put a moment of creativity into it. This took a total of 6 minutes to setup, shoot, post process and post on pbase. Yeah I might have to do a series of theses.
Here my 580EX and 550EX flahes are fired off camera by the ST-E2 that is on the camera's hotshoe.
Any EOS camera (Powershots too) can do this as long as it has a hot shoe built into the top of the camera to accept external flashes and accessories.