I guess number two on the list would be global warming (which should really be retitled global climate change). Here's a TED talk about cleaning the air with an incredibly easy to implement solution involving house plants.
Then probably a story about hybrid cars even though they aren't very viable. This is from GOOD Magazine and outlines cars and technologies you can actually buy now or in the near future.
And then they'd finish it off with a homicide story even though murder rates have been falling since the dawn of man. This is a TED talk by Steven Pinker.