I certainly wouldn't want to ride behind this light, especially on a strobe setting, so in consideration of my riding partners, I'll go to the back of the pack if this thing is turned on! It is powered by a 4 AA lithium battery pack,(I have 2) that requires it to be charged via 110volts AC, which I can get from the Sprinter van
For a headlight, I'm using a Schmidt Edelux II, powered by a Schmidt SON 28 Dynamo Hub.
This German made combo is quite bright, adds nearly zero drag, and requires no batteries! In fact, with a Busch & Mueller "e-Werk", I can use electricity from the hub to charge my iPhone, GPS, Delorme inReach, and extra battery, or whatever. It really is a pretty cool setup.
For other sources of visibility, in addition to the slow-moving farm equipment triangle like Alan has, I'll wear a fluorescent green helmet, and the very "fashionable"neon green convertible jacket from Pearl Izumi. This neon fashion faux paux is standard issue among Pacific Northwest cyclists. I also have a reflective sash that I plan to wear if riding when dark.