I got an LED headlamp from my aunt for christmas. I know it's not the most incredible headlamp in the world, but it worked for me pretty well (I've since replaced it with a Rayovac 3-in-1).
Brinkmann next to a 2AA and a 4D maglite
It runs one standard white LED on two AA batteries. I haven't timed how long batteries last, but I know it's up in the neighborhood typical for LED devices.
The unit us comfortable to wear on my head and all the straps are adjustable. The battery pack and head unit have foam pads where they sit against the head. The power switch is a click on/click off rubber-covered button on the top of the head unit. The battery compartment's construction could be beefier, but I haven't had any problems yet (and there are a lot of hacks and dings on it). A rubber band wrapped around it would keep it from popping open and losing your batteries if it got banged on a low ceiling or something, but I have never had this happen.
battery pack closed
battery pack open
The light output is comparable to that of a 2AA maglite, except it is a sharp bluish-white instead of a soft orange color:
(These are each 1 second at F3.2, ISO 100 with a Canon A70 in my somewhat dark dorm room)
The lamp came with a small convex lens built into the protective lens. It made the beam have a bright spot in the middle, about the size of a coffee can when projected at the ground from head level. Around the bright spot was an almost completely unlit donut shape, surrounded in turn by a dimly-lit diffused larger donut. I didn't like the bright spot. I need more of an evenly diffused light than a sharp spot. I devised a plan to remove the lens.
I was worried about how bright the light would be after removing the lens, but I soon found myself using the headlamp in tunnels and drains with the rubber and acrylic cover removed, exposing the reflector and LED beneath. This is the same effect I would get by cutting the lens out and I liked it, so I went ahead with it.
Initially, I was going to try to sand or grind off the hump in the middle of the window that was the lens, but getting it completely smooth and flat to optical specifications would be nearly impossible. I opted to do it the manly way and hack the whole thing off. The rubber and acrylic shield twists off of the head unit with little effort. The clear acrylic window/cover part comes out of it's black rubber housing by prying the rubber back over some barbs. I used a forstner bit to machine away the flat part of the acrylic piece. Once I had removed about 1/8", I sanded the burrs off of everything and cut a circle out of a scrap of 1/8" acrylic sheet left over from putting a window in my computer's case.
intact (but already modified) head unit
head unit with outer cover and lens housing removed. I used the light like this a lot before modifying it.
the modified lens and cover taken apart (the cutting was done to the part on the right and the new plexiglass lens is on the bottom)
I ended up making the new flat lens a bit on the small side, but it is large enough to catch on the remaining part of the old acrylic tube and work perfectly. Now just drop the new window in to the rubber part and refit the rest of the old acrylic tube in over the top of it to hold it in place. Viola; a new unfocused light.
Not a shabby light for about US$20. Here's a link to it at REI.com:
http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000&productId=47576078& parent_category_rn=4500596
