The link is dead...?
Welcome to the Learn Linux Project
I've been using this. They're in the proccess of moving the servers to a more... 'reachable' location. They also have a moodle version of the site.
Learn Linux - On Line Classmates
Again, good luck with the load times - i just download the single page HTML or PDF docs. This site is by The Shuttleworth Foundation -
The Shuttleworth Foundation