I have been looking for a Moodle + WPMU plugin that would make use of Moodle's Network Roaming feature much like the software Mahara does with Moodle.
Basically it uses xmlrpc to allow single signon and roaming from one website to another with integrating users. I am sure this is similar to the WPMU + BBPress type of plugin.
We were using Moodle + Mahara to achive a ePortfolio/social networking type of site from users within Moodle who would roam over to Mahara. Mahara really lacked a strong blogging platform for the students to use. Plus, the teachers that I have shown BP to all seem to agree it is laid out more like facebook and other tools that are easier for the students to pick up on and use right away.
Basically, we have moodle which is like a structured classroom and WPMU+BP which is like recess for the students. We'd like them to both work together if at all possible.
I'm gonna bet this is a major undertaking though.