Oregon Department of Transportation (ODOT) just released a pretty great guide for bike commuters. Though it specifically deals with Oregon road law, the suggestions are basic enough they could apply elsewhere in the U.S. as well.
The Bicyclist's Survival Guide (see the full PDF here) is nicely organized with four main sections and great safety tips in each. For instance, in the first section, "Abide When You Ride," the guide reads, "Pedal by the book. When on the road, your bike is a vehicle. That means you have the same rights—and responsibilities—as motorists. So obey all traffic signs, signals, lane markings and other rules of the road."
There's also a really neat spread cleverly called, "Check Yourself Before You Wreck Yourself":
Download the full PDF here.