While it doesn’t get as much publicity as multimedia-based sites like YouTube, I often find interesting presentation on a variety of subject (like Information Architecture, Technical Writing, Localization, and of course DITA) from SlideShare.net.
The following is a good summary of the basics of DITA by Selvakumar T.S. from Cadence. At 60 pages it belies its “Quick Start” title, but for anyone starting out in DITA and looking for some basic code examples (unfortunately not directly copy-able) it’s got all of the basics right. For beginners this is a nice overview.