I plan to try these, for my commutes in the dark this winter. On a drop-bar bike, these bar-end plug lights point rear-ward, and have steady - flash - off modes that can be switched on the fly by simply pressing on the bulb. They're super-bright, and I figure that the rear-shining light / turn signal is pretty intuitive to most motorists, who are used to seeing steady red tail-lights from cars at night, and who already know to expect a turn when one tail light starts blinking.

Nashbar Drop Bar Light Plugs

Too bad they're not Euro-style Orange.