Yesterday night, I went out for a ride with no helmet, yet I felt safer than if I'd had one.
Why? Because I had my LED headlamp and a reflective vest on. These are neat because you can get someone's attention simply by looking at them. One of my neighbors would have probably hit me on her motorcycle if not for this. This dummy was doing that thing where she starts her left turn way early. So first, she's in her oncoming traffic's lane, then she was going to cut across my lane. (she was turning left, coming from my right) I was ready to stop, but I looked right at her, and the 1W LED got her attention.
People behind me had no trouble seeing me because of my reflective vest. (my blinking red rear LED crapped out earlier this year)
This one is nice because it has a focused, powerful beam.
I have another one, a PrincetonTec Aurora that has 3 lesser, wide-angle LEDs. This one is great for being seen with, but not so great at illuminating one's path, as the LEDs aren't strong enough to light the way ahead. Here's a link that talks about that one: http://flashlightsunlimited.com/aurora.htm
These don't replace a regular bike headlight, but they're better for getting other drivers' attention at night before they get a chance to hit you.