The Walthers ones are nice-looking. I've seen them in action at a club layout open-house, and I thought they were pretty good. The price is actually pretty reasonable for the lights themselves, but the controller circuit is a bit pricey. (It will run multiple units, though.)
A company called Bakatronics at www.bakatronics.com also makes a traffic-light controller. I haven't tried it, but if I ever get around to installing traffic lights, I will give that one a try.
It takes an iron man to play with a toy iron horse.