Coggle is a freeware mind-mapping web application. Like other mind-mapping software, Coggle produces hierarchically structured documents, like a branching tree. This contrasts with conventional collaborative editors, like Google Docs, which provide either linear (text document), or tabular (spreadsheet) document formats (wikipedia). https://coggle.it/diagram/536458080588ba856a018d69/9bbcfc982921947cf145cd0d4d1a02e2aa1ab11108f771e0f859280ad2b2a771
Basecamp makes it easy for people in different roles with different responsibilities to communicate and work together. It’s a place to share files, have discussions, collaborate on documents, assign tasks, and check due dates. Basecamp stores everything securely and can be accessed at anytime from anywhere.
Free - web based - Classmint lets anyone create annotatable, audible, beautiful notes that can be folded like paper. It also maintains automated revision list to aid in timely revision. Students/Teachers can keep their notes private or publish them.
POSTICA - Online post-its with a social media twist. Students and teachers can add notes and immediately send the note to another user via email. Other users can accept/reject the note. Get notes from Twitter or email sent directly to your board. Not as robust as other online post-it collaboration tools, but it may meet some needs.