Some of the ideas around this so far are awesome. However, I did want to offer a slightly differing opinion that is rooted in the sobering reality of business today.
Often times we have budget and time constraints on what we can create. So as much as we want to offer advanced / enriched materials for the truly interested, sometimes it's just not practical. Instead we have to focus on the 90% instead of the 10%. However there is a bright side...
We've found that the 10% that want to learn more are typically are going to do so regardless of what we offer them... or don't. They are far more likely to seek out additional knowledge on their own no matter what form it comes in.
That does not mean we have an excuse to ignore them. But it does mean that if business realities rear their head, we are able to invest more time into making the main course richer and more engaging, then offer the passioante minority materials outside the course itself. Often times, we can best feed this need in a low resource way with simple collections of resources they can pursue through attachments or links.
Again, I'm not trying to dampen anyone's creativity! Far from it. Just a reminder that in some situations, it's best to focus on the majority and enrich their experience, then get out of the way of the ones that are going to learn it with or without our help.
Hope this helps and good luck with the project,