I've talked below about powdered sugar treatments, and I continue to experiment with that method as part of an overall management protocol. However, after treating a couple hives with Apiguard, a thymol-based "natural" mite killer, I experienced a reduction in mite drops of 50-66%. That seems pretty good to me, so I decided to treat the rest of my hives with Apiguard as well.
This video shows how easy and quick it is to treat with Apiguard. You simply leave this first treatment in the hive for two weeks, then replace with another packet, which you leave in until the gel-like solution is gone.
I got my Apiguard here, from Bee-Commerce. That's Howland Blackiston's website, where you can find lots of high quality beekeeping gear. He's also the author of the first beekeeping book I ever read, "Beekeeping for Dummies." I highly recommend including this book in your beekeeping library.