I'm looking forward to the development of Open Textbook projects like the one at
Connexions.
It allows instructors to produce 'modules' which roughly translate to a chapter in a book. These modules can then be packaged into a 'collection' which roughly translates into a book. The individual modules and the collections as a whole can all be downloaded in PDF format. Modules from different authors can also be combined to produce adhoc collections, and in fact the intent is for instructors to collaberate with one another. For example, three or four professors could agree to produce five modules each for a collection on a course in Statistics. Interactive material and videos can also be included, which can then be downloaded as a Zip file. The project is just getting started, but it looks like it has a lot of potential.
There is a nice youtube video about the project that was taken during one of the TED conferences.
http://www.youtube.com/watch?v=RRymi-lFHpE