Ask HN: Is there a repository of “green” tech firms?

Warning, there will be opinions in the text that follows

Climate-change skeptics please disregard this post.

As far as I see it, there is one problem in the world that shadows all other problems: climate change.

I'd like to put my programming skills to good use, meaning trying to chip away at that exact problem. But the problem is huge and there is a million angles you could (should) address it.

THE QUESTION:

Is there a list or repository over companies that work towards reducing the harm we are causing by emitting CO_2? Or maybe a place where people with great ideas can get in contact with people who have skills they need to make their a into reality?