After researching the ideal flash slave system for months I settled on the PocketWizard system. In reality, there wasn't much of a question in my head as to which system I was going to buy, this may seem a bit silly, but they had me at the ads. Their full page ads run every month in Shutterbug and many other photo mags, and their system is built in to several competing brands of lights including Profoot, Dyna-lite, Speedotron and Norman. There is fairly solid consensus in the professional photo industry that the PW system is the best you can get. The only other serious player for radio slaves is Quantum, but they just aren't as slick.
I just picked up a set of 2 Pocketwizard Plus II transceivers from Adorama and a third unit from Samy's Camera and they are nothing short of wonderful. Not only are they absolutely simple to operate, they just plain work. After about 500 shots fired, I've never had a single misfire. They are light-weight, compact, and as far as I can tell, very sturdy. They have a range of roughly 1500' and they will receive and rebroadcast signals so that range is really only limited by the amount of units you own. I recommend these units without reservation.