I already started on the flashes. (love the 640x480 camera I dug out for this?) Trial #1 Quantaray MS-1. Comes with a neat little folding stand that has a 1/4x20 threaded base and a funky strap, should you want to mount the flash on a post? Nice part is it has a built in slave sensor. Does not work with digital cameras that have a pre-flash.

Globe from Home Depot, it's plastic, not glass.

Slide the globe over the flash and bingo, you has a diffused slave.
Guide number is a guess, because they don't say!

With the diffuser it's probably down to 30 or less. Even if you use it bare or for back lighting, $19.95 is a good deal. Now I have two kicking around the office because I went to a slave that's compatable with my newer cameras.
You can make these work with any digital camera, but getting an old manual flash, that doesn't do pre-flash, but has something like the Vivitar thyristor and light sensor. It will only flash once, and will sync the camera with the slaves. Just won't work if you have a camera with a built in flash and no hot shoe.
{MORE - because that's four}