image from http://www.digitalstrategy.govt.nz/Resources/Publications/digital-strategy-2-draft/draft_collaboration/
This site has a list of 50 free collaboration tools that can help with distance education, group projects, homework collaboration, or working with other schools. The tools allow for group papers, file sharing, communications, and much more. The resources are listed by topic for easy searching.
Some of my favorites: Google Docs, Zoho, Skype, drop.io, Blogger, and Twitter.
I already use some of these, but I found some really good new ones too.