Hold online discussions.
Bounce - A simple and easy way to share comments or feedback about any website.
Convore - A site to communicate with groups of people in real-time. Groups can be public or private and accessible via the Internet or mobile devices.
Google Groups - Conversations can be done via email, online forum, or both. Groups can be either public or private, and moderated or not.
MicroMobs - An easy way to carry a group discussion without cluttering up your Inbox.
Piazza - A central place for teachers and students to post questions to elicit responses from either other students or the instructor. Responses can be 'improved upon' through either other student edits or instructor edits. Teachers can endorse student responses. A great way to encourage collaboration and peer editing!
Today's Meet - An easy-to-use backchannel site without the need for a Twitter account. Set up a room, decide how long you want the room to be active, then give your audience the room's URL. Free to use with no ads.
Twiddla - A no-set-up, web-based, meeting playground. It's web-browsing with friends...Browse websites in a shared, real-time whiteboard, while marking them up, sharing files and chatting.