Green Business News often has stories related to green IT. They have a nice review on a product from ScriptLogic called Desktop Authority. DA does many things, but one of the things is power managment. And with 36 percent of all desktop being left on all night long, that's probably something that could save big bucks.
After seeing a lot of these types of products, I'm convinced that the decision to leave a computer on all night long is a primitive one. By that, I mean that I think people really do think about turning off their computer; in fact, I think most people think about doing it every single day. But the decision to not turn it off is primal, a classic short term gain over long term benefit trade off. And since it cost employees nothing to leave their machine on, all's it takes is just one more tiny thing to make the decision ("I might need it bright and early in the morning, fast!") Again, I think most people make this decision every day.
A lot of IT decisions really boil down to just two options - you can change people's behavior, or you can have a machine solve the problem. Often I have found that the slant is towards the machine. If you feel you really need desktops (and there are many compelling arguments why you dont), it seems like you will need one of these software packages as well. The danger is that your employees may be less inclined to activitely contribute to your green efforts if they see the Technological Fix being applied, which will leave them powerless. And as we all know, something without power doesn't run very well.