Google Groups is an alternative to being on a bazillion mailing lists, and has an interface to Usenet as well.
Google Groups is not free software, but rather a web application. The debate on how free software and web applications should work rages on.
To me, Google Groups is far more like.. any discussion forum, than an application like Gmail or Google Docs.
I just joined a new group, and was presented with this:
This is really smart, and something that GNU Mailman should offer, so I filed a bug.