[Moderator Note: Since lights are so important in the winter, I'm making this a temporary sticky. Please post your bicycle light comments, suggestions, and questions here. For Home-made bike designs and questions, see Total Geekiness.]
Since so many people are starting to get lights for the fall and I was bored, I came up with this.
Edit: Updated 10/2/05 - V4
I realized since most of you commute, charge time is important, I added a column for that too. In most cases, I tried to list the lights with the charge times that come default with the unit. Faster optional chargers may be offered by the manufacturer. Also, I've included this both as an excel and HTML file. With the excel file, you can at least sort by different things. The HTML file is separated by what I think are the most helpful ways of sorting it.
Edit: Updated 10/3/05 - V4a
I added a pivot table to it. If you have office 2001, 2002, or XP, you can use the pivot table, it makes viewing it a bit easier. I also formatted the HTML file for easier viewing.
Edit: Updated 2/7/06 - V5
Changed around my ramblings a little, updated chart.
The numbers are approximate for clean roads, if your roads have a lot of potholes, debris, poor visibility, etc, please take the liberty to knock a few mph off these numbers.
Edit: 10/20/05, 11/9/05, 11/11/05
Added these links for some headlight beam comparisons.
Link courtesy of 2manybikes.
This, I think, is the best one yet:
Link courtesy of Ken Wind.
A short primer on different types of lights.
LED's (~20-30 lumens/watt)
LED's are pretty much all solid state. It's basically a computer chip that gives off light. They range from tiny blinkers that run on AA or AAA batteries to full 5+ watt lights running on rechargeable batteries.
The primary use of a blinker is to be seen. Blinkers can operate in constant or flashing modes. The latter mode of operation usually yields the greatest visibility for the cyclist due to the conspicuous nature of the strobe. Another advantage of that mode is the diminutive draw on the batteries. The batteries can usually last days in this mode. Unfortunately, the lights are too weak to be used to see at high speeds in their constant on mode. They are generally good in extremely dark situations when going slowly.
High powered LED lights usually start at 1 watt and go all the way up to 5 watts per LED module. Some lights have multiple modules. Since there's no filament to heat up or break, LED modules can typically be set to either a rapid flashing pattern to attract attention or be run on a solid on mode without risking damage to the bulb.
The color of the LED's are usually white but they can vary from having a slight tint of blue/green to being purplish.
Battery life from most manufacturers range from 2-5 hours for lights running in extremely bright modes to 10+ hours of usable light and 30+ hours of dim light to keep the rider visible.
Virtually indestructable and virtually infinite (50000+ hrs) life.
Can be powered down significantly to achieve DAYS of run time.
Lights are relatively expensive (for now).
Halogen (~10-30 lumens/watt)
Halogen bulbs are basically "space heaters that give off light as a byproduct." (ha ha, laugh!)
They heat up a metal wire to produce a lot of heat and also give off light. Most production lights will either run a MR11 halogen bulb and reflector unit or have a custom reflector and use just a bulb. You can often find a large variety of off the shelf MR11 bulbs to fit your individual needs. The lights can range anywhere from 5 watts to 30+ watts. Some companies have electronic controllers that enable a single light to run a range of wattages from 5 to 15 watts.
The color of the lights can range from a yellowish glow to a bright yellow/white light.
Battery life can range from an hour for lights running in extremely bright modes to over 4 hours in lower power settings.
Lots of different bulbs out there, cheap to replace.
Lights are relatively inexpensive.
Relatively short battery life on high brightness.
Filament can break under extreme shock and vibration.
HID's (~50 lumens/watt)
HID lamps basically use a tiny bolt of lightning as the light source. There's no filament, only a spark ionizing a tiny gap between two electrodes. These lights all require a ballast control system that usually comes built into the lamp housing itself. The lights are equivalent to 1.5-3x what a MR11 can put out in terms of light. Since there is no filament to wear out, the lamps usually last many times longer than a halogen lamp if left on. However, the process of starting the spark in the HID bulb wears out the electrode each time and as a result, cuts down on the life of the bulb. Most bulbs are rated for 1000 hours & starts.
Manufacturers usually put their best into these lights and as a result they also get the best battery packs. Run times at full brightness can range anywhere from 3 hours to 12 hours.
The color ranges from white to white with a bluish or purplish tint.
Bright white light.
No filament to break.
Relatively long battery life.
Require a 20-30 second warm up before reaching full brightness.
Starting and restarting the lamp cuts down on the life of the bulb.
Require a minute to cool down before turning back on if turned off.
Thin glass bulb still subject to breakage under extreme shock or vibration.
Relatively expensive bulbs.
Relatively expensive lights.
Most active rear visibility devices nowadays are the standard battery powered blinkers. They perform adequately in getting the drivers attention from directly behind you but there are also several on the market that give you visibility from the side. These can either be in blinking mode or solid mode. Blinking uses less battery power and also attracts attention better. However, it is more difficult for the driver to pinpoint exactly where you are and where you are going since there isn't anything consistent to reference from. Also, some blinkers blink extremely slowly and a driver may miss you if they are quickly scanning across the road. It's best to run two blinkers, one on solid and one on blink mode.
One of the better ones is the Cateye TL-LD1000. It has 2 rows consisting of a led on each side and 3 LED's facing rearwards. Each row can be independently set on blink or solid.
One of the brightest ones out there is the Niterider tail light. It contains up to 19 LED's in a very small package since it's powered externally. You can either plug it into a splitter powered by a niterider headlamp battery or cut the power cord to rig it up to your own battery. My recommendation is 9+ volts for adequate brightness.
Here's a video of the NR in action courtesy of MechBgon next to the TL-LD1000.