"an open source social platform based around choice, flexibility and openness: a system that firmly places individuals at the centre of their activities. Your users have the freedom to incorporate all their favorite tools within one environment and showcase their content with as many or as few people as they choose, all within a social networking site that you control."
In August of 2006 ELGG Spaces was about ready to launch, it allows any one to sign up and have a tailored environment for their organization. This seems like it would be great for teachers because it allows teachers to create a space specifically for their class, however they are no longer accepting new sign ups.
Some Universities are using Elgg as a private blogging site, some as a course management tool, and some as a campus-wide social network.
Example: University of Brighton