The ideas behind Learnfab came in part from helping my son (now age 8) learn German. One aspect was predictable: it's important for learning to be at least somewhat fun. But the other key issue was somewhat of a surprise to me: assessment (testing) is vital for self-paced learning. It's hard to do by hand, so should be deeply embedded into the e-learning process. See the Results section of the tutorial for our current implementation.
The site has some rough edges and there are lots more features to add. Meanwhile I welcome questions and comments.
P.S. Thanks (in alphabetical order) to Andrei, Armin, Bob, Brenda, Julia, Kim, Kyle, Peter, and Rod for work on Learnfab and related projects.