The most commonly used reference for dynamo lighting is the Peter White site, which includes pictures of the lights -
http://www.peterwhitecycles.com/headlights.asp

If you've spend the money on a good hub and a wheel and you want the most light possible it usually comes down to either the Lumotec Cyo (a nice light with a shaped beam that really does a good job lighting up the road, but doesn't light up off to the sides much) for around $110 or the Supernova E3 (Symmetrical) which is the usual more "round" beam for around $220.