Web 2.0 and Grad School

Here are some great neccesities in the whole Web 2.0 space:
common virtual space
open access to services and data
user-defined structure and tools
simple applications and services

The web can be a great place for Grad School classrooms,students and organizations to converge for learning,sharing, and educational development inside and outside the classroom.

Do you have any favorite apps that you would like to share post them in the comments.