'Communities (of practice) are everywhere and people generally participate in a number of them', according to Etienne Wenger (http://www.ewenger.com/).
The UvA communities (University of Amsterdam) aims to place this important observation in the context of the 21st century University, by creating a ubiquitous community platform that is able to stage a number of different communities and users, including individuals from outside university. Within one system, users can become a member of one or more communities, and communities may be formed around a number of topics, ranging from a general field of studies to an ad hoc problem area.
Unlike most information systems in educational organizations, UvA communities (http://www.communities.uva.nl/)is open to the public and is free to use. It's very purpose is to allow people from outside the university organization to connect within the realm of the university and to give insiders means to easily connect outside university, all having access to the same set of tools and services, which are extensible with tailor-made functionality. People from many different cultural and scientific backgrounds collaborate on a variety of topics and take on multiple roles in multiple communities.
UvA Communities started as a pilot project in the autumn of 2006 at the institute of interdisciplinary studies. Together with a small company Edia ,the
UvA communities hosts some very interesting use cases.