If you have to drive a longer distance at night, you are bound to run into people who don't give a damn about other cars and won't dim their lights. Although it's usually harmless, ocassionaly it can result in accidents, so if you're in the "better safe than sorry" crowd you could try out something like the Anti-Glare LED Visor.
(the link is a Google translate of the original German website).



The LED panel attaches to your sun visor and softly illuminates the inside of the car at night, thus causing your eyes to stay adapted to light. Your pupils will shrink slightly, so you'll have less of a problem with bright incoming lights. The brightness can be manually adjusted until you are comfortable enough or you can just use a set of ambient light sensors.

via.