Identi.ca

Identi.ca (launched 2008) is an open source social networking and micro-blogging service. It uses the software StatusNet (licence: Affero GPLv3+).

Some advantages to use identi.ca are:

all notices are published with Creative Commons Attribution 3.0 license
better view of replies (example: identi.ca, click hell at twitter: [1])
one can forward messages also to twitter
FOAF (Friend of a friend) support: a machine-readable ontology describing persons, their activities and their relations to other people and objects. example: [2]
when you install your own StatusNet instance you have control over your data (e.g. you decide with whom to share or not, ...) + can connect with other network systems (e.g. twitter, ...) via federation
...

Wikiversity related info on identi.ca

tag #wikiversity: you can generate these when you add in your message #wikiversity
group !wikiversity: you can post here when you add in your message !wikiversity

(alphabetical)