I'm currently using a "Coast Micro Headlamp"
(http://www.utilitysafeguard.com/LL7451-Micro-Headlamp)
It's bright enough to read cues and people have said good things about
the green LEDs on the back. It stays on the helmet using the elastic
band. Not an amazing light but it cost $15 and gets the job done.
I've also had good luck with cheap headlights at Home Depot coupled with
a Velcro strap to hold them on. (Yes, I know I shouldn't do this.)
Jake
(I need to turn this into a blog post or personal FAQ)
Being on my third helmet the last three years I'm a big advocate of
not permanently attaching anything to the outside of my helmet. I do
think that depending on the type of riding you do, having a helmet
light can help you avoid a collision with a vehicle/animal/pothole in
the first place and make up for the danger of having a protruding
object.
I use a homebrew generater powered LED for my main light, but for
reading signs, seeing around corners, and getting attention of drivers
I use a Fenix P1D-CE Cree Q5 flashlight that I zip-tied to my
helmet. With the flashlight firmly wedged into my helmet vent I can
turn the front easily with one hand to turn it on/off and adjust the
brightness. On medium (96 lm) it will last about 3 hours on one 123A
lithium battery. It'll go about 21 hours on low (16 lm), which is
still plenty bright for reading street signs on a dark road. High is
obscenely bright at 180 lm but only lasts an hour. I save that for my
fast descents.
https://www.fenix-store.com/product_info.php?cPath=22_65&products_id=354
During PBP, with my main lights attached to the bike I found myself
not using the helmet light at all except for descents.
I carry a little baggie of extra 123A batteries in my trunk bag,
enough to last the entire night part of any event on medium.
http://img.stimpy.net/pics/bike/lighting/640x480/IMG_0062.JPG.html
It took some trial and error to get the angle right. I wanted to have
the spot of the light in the center of my vision so that I could look
around naturally and have it follow me. I ended up wedging some rubber
pieces under the front of the light to get the angle right. I also
added some waterproof grease to the O-ring to allow it to turn easier
and keep the expensive flashlight waterproof.
The new Cree is the currently most efficient LED flashlight you can
buy, and the Fenix P1D-CE Q5 is a very highly regarded flashlight.
If you want to go brighter you can get an Cree MC-E powered
flashlight, but it's bigger, heavier, and takes hard to find
rechargeable batteries.
http://www.dealextreme.com/details.dx/sku.16540
For reading computer/cue sheets I use a Photo Freedom red LED light
velcroed to the front of my helmet. The red lasts much longer than
white, and doesn't mess with my night vision.
It claims to be waterproof and survived a very wet PBP with no issues.
While we're talking about illumination, I also recommend picking up
some red reflective tape for the back of your helmet, rack and
seatstays. It makes a huge difference for drivers coming up behind
you. I don't understand why all helmets don't come this way.
http://img.stimpy.net/pics/bike/lighting/640x480/IMG_0065.JPG.html
You can find a great selection of reflective tape at reasonable prices
at http://www.identi-tape.com/hi-intensity.htm
In addition to putting red on the back of my rack and the back of the
seat stays, I also put 1.5" of white tape between every other spoke on
my rims. This leads to the appearance of two solid white hoops, and
I'm told that it's still very visible even from nearly directly
behind.
Joe
Emily