You need a good front light to see as much as be seen. Riding in the dark makes you very vulnerable to obstacles on the road such as potholes, sticks and gravel.

I've got a Cygolite NiteRover and it is a very good, reliable light for not much money. You can buy one for about $70 including dual lights, NiMH battery, and a charger. You can use the low beam only for visibility, the high beam for illumination, or both for maximum light. Charge times are good, particularly on low beam.

Some of the new LEDs look pretty nice, but I don't have personal experience with them. If considering LED, the Fennix lights seem to get a lot of good reviews. They can be used as a flashlight as well.