Have you ever wanted to use multiple speedlights together for more output or faster recycling time, but don't have two receivers for them? I made a post a few days ago showing my double speedlight setup in a Photoflex Octodome. I use the two speedlights together for more efficiency and redundancy. I also connect two PocketWizard receivers – one to each speedlight, so that I can assign a zone to each speedlight in the event I want to quickly turn one zone off from camera position – effectively dropping my total light by 1 f-stop. However, not everyone needs to do this and not everyone has an extra receiver to spare, so here's a cheap and effective solution.
Most of us have headphone splitters hanging around our gadget bags so we can share music with a friend from an iPod. The same splitters will also work to split the signal from one PocketWizard to multiple speedlights. In fact, by chaining two splitters you can share the signal with 3 speedlights, as shown in my example photo. It's theoretically possible you could split the signal even further, but I haven't tried to see how far it can be split before signal loss occurs.
You can get a headphone splitter at almost any convenience store in airports or your local electronics store. Using this setup, you don't get independant zone control, they all just fire together all the time. Usually, however, this is perfectly okey dokey and a simple way to trigger your speedlight arsenal!