Valve just uploaded all the talks from Steam Dev Days, the event they held recently about Steam and Devs and uh, other things. Some seem a bit dry as you might expect from people who spend a lot of their time working on games and not talking to crowds but they all hold up well, haven't seen any incoherent rambling so far. The couple I've watched a significant amount of are pretty interesting, especially the ARG one which I was really interested in as Ive been a part of a couple of their past ARGs.

If you're intrigued you can find them all here: www.steamdevdays.com

hmmmm, personally for me the best valve presentation was TF2 art direction. I use that one as reference source and has helped me as an artist. Although Early access talk has Jamie Cheng of Klei Entertainment, so that's fascinating to hear from him out of all people out there.