Connexions, Rhaptos, and Plone each look like something to explore in more detail. But first, here are just a few words on each, given in the order that I stumbled upon them (because Connexions is built on Rhaptos which is built with Plone).
Connexions is a collection of “knowledge chunks” freely available to anyone. At first glance it looks a bit like Merlot, but adds more as it allows students or teachers to actually pull together different chunks into their own course structure.
Connexions is built on Rhaptos, an “educational content management system”. The software was developed specifically for Connexions, but is also freely available for download for those who wish to build their own content repository.
And finally, Rhaptos is built on Plone, a CMS that is relatively simple to use, also available for download (open source distributed under the GNU GPL license).
So many goodies, so little time… 😉