+1 for Cygo's. They are bright, light and effective and as Bulldog said, USB so can be recharged any number of ways. I especially like the Dash model as it's small, quick to mount and portable. One thing is for sure about Cygo's, the strobing feature is something that motorists CANNOT ignore. I know, I'm a motorist!

The ones that cyccomute mentioned look very promising and I may order one since it's around $20 bucks.