After 15 years with the big-ass Quantum radio slaves, I got a $15 Yongnuo set from Amazon - for the bucks, really reliable. You have to watch line-of-sight to some extent, but hard to beat for the price.
BUT - some older gear that works fine with the Quantums won't fire the cheapies. All my Mamiya RB shutters, my Spotmeter F, and my Sekonic won't trigger the Yongnuo. My 4x5, all my 35mm SLRs and RFs, no problem. I think some synch circuits must be too butch, have too much resistance, something (ever seen an RB sync circuit? Big chunks of metal in there).
I finally broke down and got a used Pocket Wizard set for like sixty bucks. Why I didn't do that ten years ago, I dunno. works fine with everything.