I still think that there's something to be said for mere social interaction, which may indeed turn into some small scale class-type discussion. To that end, I have begun to create an area in the hellyeah.com moo to be used for discussion and learning which I have modeled after theBrown University Center for Information Technology. It is still wildly incomplete, but it might give a sense of a setting that might be used as an academic setting.
To connect, telnet to moo.hellyeah.com port 7777. If it is your first time connecting, you will need to create a new character. Once you are logged in, you will be in the washroom. In order to get to my area of the MOO, you will need to go east, then south, then south again, east again, then north. You will then be on the patio of the CIT.
For a busier, more developed environment, try LambdaMOO, the first MOO. Give yourself a couple of hours and log in and explore. Talk to people. You'll be surprised what you feel after you've been there a while. I know I was.