This is a pretty cool tool http://www.verdiem.com/edison/ for WindowsXP and Windows Vista. It is really nothing but a more intuitive interface to the Power Settings you can access through Control Panel. You can tweak all of the power settings and more using the control panel, and most laptops now come with some fancy tools for doing the same thing, but this little application does a nice job of using a slider to adjust based on how much savings you would like to get. It also shows numbers in terms of money saved on your electric bill, Energy and Carbon output.
It uses a Work and Non-Work time, which like a programmable thermostat is a pretty nice concept but in our busy schedules I am not sure how much you can apply standard times.