i consider running red lights to be an essential safety technique for urban riding. after running a red light, and especially after sneaking through a light right after it turns red, you find yourself on a completely vacant street. no cars = no threat. the more often you run red lights the greater the percentage of time you spend on empty streets.
here's some knowledge that i find useful: on new york's one-way avenues, the lights are timed in groups, divided by the major crosstown streets i.e. 14th, 23rd, 34th, 42nd etc, and they're timed for 20-25 mph traffic. Thus a bicycle riding down seventh ave will begin hitting yellow lights, then reds, because bikes aren't fast enough to take advantage of the lights' timing. However, the cycle restarts after every major crosstown intersection, so that if a cyclist can make it through the light on a major crosstown, the next light will be not red, but green, and an early green at that. So if you can sneak through a red on a major crosstown street, you'll get 5-10 blocks of clear sailing with no cars anywhere near you.