A little over three weeks ago, Valve hosted a fairly big developer conference, which excluded journalists so that attendees could network without feeling anxious. The goal was not to keep information from the public, however, and so they created high-quality recordings of the talks and the Steamworks Development YouTube channel, which I assume is owned by Valve but cannot verify this, made the videos public.
Again, each of these talks were aimed at various types of developers, and they were hosted by numerous companies. One video has Tim Sweeney, the founder of Epic Games, discuss Physically-Based Rendering (PBR) and another has Na'Tosha Bard, the technical director at Unity, highlight points that a game developer should know if they intend to publish to Linux, including SteamOS.
In all, there are 25 videos, ranging from ten minutes to an hour and a half, with most clocking in around 45 minutes. It's a fairly large commitment if you want to watch it all, but the topics vary wildly, so it could easily be a “kill an hour learning something” sort of thing. Also, the talks from 2014 are available, too. (There wasn't a Steam Dev Days conference in 2015.)
Thanks Phoronix for finding these.