A Scratchpad has a variety of communication tools which perform different functions.
If you want to write short periodic updates then you want to use a Blog. For longer updates, you may want to consider using Newsletters.
Do you have a community site? A Forum will allow your users to discuss various topics in one place.
Comments can add value to content on your site and can be set to allow anonymous users to comment (with moderation) or just verified users.
To create private access areas for specific projects or manuscript preparation you may want to use groups.