I have produced a Flash tutorial that explains DITA topics, concept, task, and reference specializations, and DITA maps.

http://www.ditausers.org/training/DITATopics/

I am also working on Flash tutorials that explain the DITA Users website and toolset, including the DITA Manager for each member's workspace folder.

http://www.ditausers.org/training/DITAUsersWelcome/

Critical comments appreciated. This is a work in progress.