user created groups/communities

I have been looking for a CMS for a while that I can use in school. We want students to be able to blog, upload podcasts, and write wikis. We have already tried Elgg and drupaled, but are still looking for something that works the way we want it (both these distros fall down when it comes to wiki implementation).
In order to encourage student participation/use, the social networking side of things has been something that we've been looking at - both the distros that we have tried allow users to create their own groups or communities; equally, staff can create course groups that students subscribe to, allowing docs and work to be only viewed by members of the group.
Is there a way to do this in bitweaver - so far, I can see that it would be possible for the admin to create a range of groups and that users could ad themselves to them, but I have not seen a ref to user creation of groups.

Any ideas welcome - thanks!