I have bar-end mirrors on my drops. They aren't very useful, since I have to drop my head to see them, and they don't provide a very wide field of view. They are a pain to get set in the right spot, and like to ride in the drops, so I tend to knock them out of position pretty quickly. I haven't even bothered using them most of the summer since it seems a lot easier just to glance over my shoulder than to drop my head to see the mirrors.

What do people do for drop bars? I don't know of a better option, aside from a helmet mounted mirror.