We touched on it briefly here, but I think it's worth highlighting the relatively new Exchange-traded Fund with the ticker PBW that tracks the ^ECO index, also know as The WilderHill Clean Energy Index. As the name implies, the index and it's ETF allow you to buy into a portfolio of companies that are pursuing clean energy development. It's the easiest way I've seen (just purchase PBW through your brokerage) to date to get good exposure to a broad array of technologies that the TreeHugger mentality supports. Companies in the fund include Evergreen Solar, Distributed Energy Sys, Ballard Power Systems, Kyocera Corp Adr, and 30+ others. The full list is here. Anyone have any thoughts on the other companies?