Ah you can dim any light with enough work and $

But seriously it depends on the type of light, regular incandescent or halogen can go on a regular dimmer. Fluorescents need a special ballast to dim, I wouldn't recommend going that way. Led's can dim quite easily and unlike most other lighting options LED's actually get more efficient as they dim. So running a regular LED at 50% power will typically get you about 40% less light, while running an incandescent at 50% power will get you about 80% less light.