Biking in DC: #1 Be Seen at Night
My suggestion is a rear red blinky light and a front white light too. It would be stupid to get struck from the back because you weren't wearing a red blinky.
That said, most crashes that occur at night happen when an automobile crashes into the side of a cyclist. My bet, though, is that it is probably a car pulling out of a driveway, not seeing the biker. This is the reason that I wear a white blinky light in the front when I'm in the city. A steady light is great for trails or dark roads
Most new bikes come with ugly reflectors in the spokes of the wheels. Those are dorky and should just be ripped off before they break off. If you feel like you need something for the sides, get creative! LEDs and such can be a lot of fun. Like spoke lights, pedal-powered wire lights, Orbit wheel lights from Cat Eye, or... you let me know!