Nick Bostrom gave an interesting talk on existential risk reduction at TEDxOxford 2012, which has recently been uploaded at http://www.youtube.com/watch?v=P0Nf3TcMiHo and has the rather ominous title "The End of Humanity". I suppose most of the people reading this will be quite familiar with the concepts (and the talk is aimed at people who aren't), but it might be a good resource to point people to who need introducing.

Full disclosure: I am involved with TEDxOxford, though I wasn't involved with TEDxOxford 2012.