Seeking the Right Environmental Cause to Support?

Bakajin asks: "I have always been a passive environmentalist. I think that any intelligent person must have concern about our planet and the future of our species upon it and that the Slashdot crowd has many such people. I have increasingly become more concerned about global warming as more and more signs seem to point to its likely effects. I try to make changes in my personal habits but, like many Slashdotters, don't have much time to try and effect larger changes to policy and science. I do however have money. I want to know what organizations Slashdot members think are most worthy of contribution and will give me the most effect for my money, politically or scientifically. This question fits well within Slashdot because it seems to have many members who think critically about the world and their role within it. There also seems to be a willingness to openly express mistrust of the same large corporations that either ignore environmental issues or outright cause them. Please don't turn this into a debate about whether global warming is an actual threat or how bad other environmental issues actually are, but rather about which organizations are the most effective and trustworthy for me to give my hard earned cash."