Assignment Blogs allow:
….teachers to post assignments for the class and later grade them in a private secure setting. Students can work on assignments over multiple online sessions and then submit them when they are finished. Teachers can subsequently grade the assignment, offer guidance or comments, or return the assignment to the student for further work.
cMail is an e-mail-like option which provides an internal means of exchanging messages without the need for e-mail addresses, similar to features in PBWiki and Wikispaces. While the creator of ClassChatter characterizes it as a site for protected blogging, it seems to me to be more similar to use of a private wiki, offering the same basic features and the advantage of being easier to setup a class workspace.
ClassChatterLive (https://www.classchatterlive.com/) is a considerably more sophisticated version, with upgraded features, such as the ability to upload and distributed podcasts, electronic drop boxes, and permanent archiving. ClassChatterLive is available for use by all teachers in a school for a single price, $150/year; an individual account can be purchased for a fee of $30/year.