My last job was at Brown University, and they used many methods of social media to reach students. It was the easiest way to reach students, since many came from outside the Rhode Island area, and many were out of the country.
The link above gives information and graphs on how social media is used by schools. They usually use Facebook,Twitter, LinkedIn, Blogging and Message Boards.
They are used for such things as class announcements, school pride, for potential students and professional development.
I have “friended” SNHU career development office, for updates on jobs,and to learn more about updating my resume and various companies.
The above link is from the Brown.edu website which gives information on the various types of social media that is used.
Brown reaches their students thru Facebook, Twitter, YouTube, Flickr, itunesU and LinkedIn.
In my previous position, I was an assistant to a professor, but did not personally use any of the social media, other then contacting the students via email.