TodaysMeet

Another gem I found from Russell Stannard is TodaysMeet.  There cannot be a quicker way than this of opening up a channel of web communication, (which can include a twitter feed) for any kind of event.  It immediately gives your audience or your students a place to discuss.  No log on and no sign in (so not secure in any sense) but simplicity itself.  If you are brave enough you could project it as you speak to a (connected) audience, picking up immediate feedback or questions  from them live on the screen.