One thing to keep in mind is that no matter what kind of light bulb you use, it will always be worse for the environment than using no light bulb at all. Even the most efficient light bulbs draw power that comes from dirty coal. The first step to being truly green is to look at all the things you are lighting up and figure out what you can get rid of.
Another aspect of the equation to consider is that light bulbs are industrial products that are manufactured and shipped around the world. This supply process takes huge amounts of energy. New energy efficient lights are great, but whenever you can just turn the light out.