If you want to use Canon flashes with radio triggers, and you don't want to fork out for the new version of the 580EX which has a PC socket, then you need to use a PC-to-hot-shoe adapter. The ones that most people use are those made by Kaiser and Hama, but they both suffer from the same huge design flaw: The PC cord is hardwired in to the adaptor. That's fine for a while, but inevitably the cord will be tugged once too often and you'll end up with this:

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(The scratches along the side of the hot shoe are a result of my feeble attempts to prise it open so I could solder the thing back together. Yes I know there are screws on top! But they're those ultra-tiny ones and I don't have a screwdriver that small.)

After my Kaiser adaptor broke, and then my Vivitar 285HV broke, I was left without any way of firing a portable flash with Pocket Wizards. This didn't matter much at the time because most jobs were inside so I could use my studio strobes, but as the weather gets nicer there are more and more outside photos to do. So I set about finding a couple of hot shoe adaptors. But the Kaiser and Hama units are £10 each and I didn't want to throw away another twenty quid on something that I know is going to break sooner or later.

Then I found this little beauty… 

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The box describes it as a "Sonia all purpose hot shoe (3 piece kit)". I don't think any photo stores or web sites sell them and the guy I bought them from on eBay (here) only had two left, both of which are now safely ensconced in my camera bag. But if you can find them then I'd say they're the ideal solution. I paid the same price for my two as I'd have paid for a couple of Kaiser or Hama units.

Left to right in the photo: Dual purpose hot shoe adapter. You can either plug a PC cord in to it and use the adaptor to fire a flash, which is the use that we're interested in, or you can use it to convert a camera's hot shoe to a PC socket, for cameras that don't have one.

In the middle is a standard male-to-male PC cord, easy and cheap to replace if it gets damaged. And on the right is an adaptor that gives the hot shoe a female screw thread, for mounting on a tripod or light stand in the usual way.

My only criticism of this adaptor, and it's a minor one, is that the plugs on both ends of the PC cord were a very tight fit to start with. But after just a week they have already slackened off, while still holding firmly. Just be careful not to damage the plugs or the sockets because you will have to use a good bit of pressure at first.

So overall I'd say that if you need to give your flashes a PC socket then these are the adaptors you should be looking for. They're worth the search.