Power supplies can be energy hogs, and there hasn't been much motivation to do anything about it. Until now. Ecogeek is reporting that Energy Star is requiring that all power supplies be 80% efficient (or 80 Plus.) Until now, the motivation to keep costs down or build super-powerful machines has kept manufacturers tied to inefficient power supplies. This new criteria for certification, may change their tune.
Another cool development mentioned on Ecogeek is the addition of the Marvell chip to control power efficiency. Slated to appear in early 2008, it's a factor to keep in mind if you're purchasing a new machine in the next year.