A while ago I wrote about a great little Digital Media Primer from Xiph.org. Well, the follow up video took a little while longer to appear than I anticipated or as is ironically stated on the website 'Continuing the "firehose" tradition of maximum information density'. Regardless, the second video is well worth watching as it is both educational and presented in a entertaining manner.
Links to the video in various formats and a discussion wiki can be found on this page.