Before I went with dynamo lighting I used a Cateye Single Shot 1w LED rechargable. It provided decent illumination and was good for about 2 hours in High mode. I still use it as an aux light and the nimh battery is still holding up. It takes 5 hours to charge though.

Consider a dyno hub. It's a bit of an effort to build up the wheel but once done you have great lighting with no worries about batteries. Yes there is some drag, but I challenge anybody to feel it when riding.

-G