Of course, having some good bright lights is a must for being visible at night! The Bicycles Stack Exchange Blog now has the most comprehensive bike taillight review on the internet (to our knowledge):
#Review of the Best Bicycle Tail Lights in 2012
Review of the Best Bicycle Tail Lights in 2012
In total I reviewed fifteen different tail lights. The Cygolite Hotshot performed best in the most categories, but there are several other lights which did quite well. If you're looking for a good rear light, check out this review.