A few days ago, I posted about Rust, having just watched a wonderful talk about it at Scaladays. That presentation is now online. It's highly recommended for all programmers who are interested in language design -- it's a lucid talk about the language, focused on the rationale behind it and how they achieved those goals. Exciting stuff: Rust is probably the first language since Scala that I've found really compelling, the C++ replacement to Scala's Java.
And from the same series of videos comes this talk from the creator of Jepsen -- again, nothing to do with Scala, but a great technical talk. I tweeted that this one was "Funny, educational and terrifying". (The laughter isn't much picked up by the microphone, but was pretty loud at times.) Jepsen is a toolkit for testing distributed databases, and this talk (illustrated entirely with hand-drawn slides) goes into fairly deep detail about why it's so hard to build them. The upshot is that nearly every new-fangled DB turns out to be seriously broken in at least one or two respects. A great talk for anybody who is interested in distributed systems architecture. (And anybody who is using any of these databases.)
(And yes, there was one keynote that was actually about Scala -- Martin Odersky talking about "What to Leave Implicit". Also a good talk, but mainly interesting if you already know Scala; the other two don't require as much background...)