I've written about these collaboration tools before, but thought I'd do it again because they can be incredibly valuable for students doing group projects. Set up accounts and share the writing with Writely and websites with Del.icio.us.
Writely.com An online word processor which can be used by multiple co-authors. Register and add group members emails.
Del.icio.us Share bookmarks with others in your network. Add "tags" as subject headings.