Scriptorium, one of our partners in the US, has launched the LearningDITA website.
It is a free and basic e-learning course for anyone who wants to learn DITA. You learn about the DITA specification and the different topic types in DITA, and also how to make bookmaps.
The course itself is written in DITA, making use of the DITA-specialization for e-learning.
More info on the website: http://www.learningdita.com/about/