Yes, I use a Vivitar 283. I put a hotshoe-to-PC socket converter on the Holga and connect my Vivitar 283 mounted on a flash bracket with a PC cord. It works quite well, of course I made both of my apertures, so I can calculate proper flash exposure assuming that the shutter speed is approximately 1/125 s.
I've used a regular Canon flash & I set the flash output using a flash meter assuming F/8 & whatever the film ISO & distance were. Good results.
I've also used Holga to fire multiple studio flash heads using a hot shoe adapter that has a PC socket. That also worked well.
The one thing to know is that the Holga shutter fires the flash twice, first when the lever goes down & again when it comes up. The second flash doesn't expose as the shutter is already closed but it is distracting.
Umm, you realize the holga hot shoe is nothing special right? It is just a normal old hot shoe, anything will work. That said, I have a bar with a pair of vivitar 283s on it. I use this setup on just about everything. They both have vari power modules on them, so on the holga I just dial them back to an F8 exposure.
Sure, it looks pretty impressive. I can get a picture this weekend, either my friend took one and has it developed from some time ago, or we can fish out a digital camera. I should keep a copy of it anyway. : )