Corsair

Corsair, maker of power supplies (PSUs) for computers, has a full line of PSUs that have been certified as 80 PLUS, meaning they are 80% or more efficient at loads of 20 to 100%. This means your computer doesn't waste as much electricity by turning it into heat as less-efficient PSU-based computers do. The power supplies are available now (in fact the computer I'm writing on has one of them installed, chosen exactly because of its high efficiency). The EPA is pushing the improved energy standards with EnergyStar 5.0. Good for them!