OSCON Java videos on YouTube
By alexismp on Jul 27, 2011
These are short 10 to 20-minute presentations. The Twitter Java case-study is probably the most popular one so far (although YouTube seems to have some issues counting views) but you should probably spend time watching Steve Harris' "Open Source, Java, and Oracle -- Cracking the Code" to find out all about the POSTL (Perceived Open Source Threat Level).
Other interesting videos include Joe Darcy's very fine "JDK 7 in a Nutshell" (possibly the best presentation title at an O'Reilly conference) or Josh Bloch's "Java: The Good, Bad, and Ugly Parts". I have to say that I started watching one and ended up watching almost all of them.