So, I have mixed feelings when I read that Google and other large enterprises are greening themselves -- in part -- with carbon offsets. The idea of being "carbon neutral" while still burning fossil fuels doesn't seem quite right. To its credit, Google is doing many things right, and in that sense it is leading by good example. Google's 1.6-megawatt solar panel generates 30% of the peak power necessary to fuel the building in which it's located, and it's investing in numerous renewable energy projects around the globe.
Because of Google's size it will have more impact, good and bad, on green computing than most companies. However, I thought it would be worth pointing out those companies that are achieving carbon neutrality by using 100% renewable energy: Green House Data, Affordable Internet Services Online, and Solar Energy Host.