I used google groups before - and news groups before that. I like piazza best - it's made for this purpose.
I love using Piazza for answering student questions; the user interface is unbelievably nicer than anything else I've seen. It is easy to enter text and easy to see what questions need answering; It is just easy to use.
Thank you for Piazza! It has been an excellent resource for our new introductory biology courses here at Yale. Piazza is a great forum for those students who are too shy to ask questions in class and who post anonymously - and then this benefits all the students who read the answers. Plus, I have had students say that they love how quickly their questions get answered, instead of waiting for office hours or the next lecture.
Instructors can create a Piazza for their class with a single click.
Students and instructors are automatically enrolled with appropriate roles, based on the course roster.
When clicking on Piazza in Howdy, users are automatically signed in to Piazza, so there's no need to remember a separate user name and password.