Apple is one of the of the largest [non-utility] clean energy generating companies in the country. According to a report from March of this year, it's achieved 100% renewable energy in all of its data centers, and 75% in corporate buildings.
Of course, its crown jewels are the solar panel and biogas fuel cell farms that run its Maiden, North Carolina data center—two of the largest of their kind in the US. And a recent report from GigaOM takes a closer look at these NC facilities...