In their words:
Wiggio.com™ is a free, simple group collaboration website for students. Wiggio provides students with a toolkit of functionalities that among other things, makes it easy to share documents,communicate within groups, schedule and remind people of events, share resources, and get a quick consensus among group members. Wiggio’s key strength lies in its simplicity— the goal is for Wiggio to be the easiest way for students to work in groups.
This is not a social networking "me too" site, but a productivity tool geared towards the modern mobile student. Check them out. It's free, useful, and simple.