I run the new 2 AA 3-watt Mini Mag-Lite myself. Considering the cost is slightly more than $20 it's an extremely good deal. It produces enough light to actually see where your going and the adjustable beam allows you to tailor it to your night riding conditions. Wide for dodging stuff in the parking lot and nice tight long distance beam for on the road. It also does not have the "dork factor" of a bike specific light that forces you to mount the light to the top of your handlebar. As for mounting, that’s very easy! Just use EMT conduit hangers available in the electrical supply area in any good building supply store like Lowes. I use contact cement to attach small peaces of rubber in the clamp so my flashlight and handlebar does not get scratched up. Below is a photo of my Mini-Mag LED light on my road bike handlebar.

On this setup a plastic clamp from an old blinkie is used on the handlebar and the EMT conduit hanger "clamp" is bolted to it utilizing a 1/4-20 screw and nut which also tightens the clamp to the handlebar. I had to drill out the clamp to use the larger screw and nut.

Battery life is short when compared to other not so bright LED lights at 2.5 hours on standard alkaline batteries but for most of us this is adequate. If your going to run all night and don’t want to stop to change batteries simply load it up with 1.5-volt Lithium "camera" batteries which will provide about 17 hours of continuous burn time.

Here is a picture of my Flashlight and two EMT conduit hangers ready to clamp to the handlebar of my touring bike.