There's Google Groups, of course, which seems to have reinvented itself yet again. I copied this from the 'what's new' page:

New Groups includes most popular Groups features as well as:

*Improved navigation—Group settings are consolidated into one section for easy access.
*Streamlined group creation—A three-step wizard simplifies group creation.
*Powerful search options—New filtering and search options help you find content.
*Simplified My groups page—When you’re signed in to Google Groups (groups.google.com), you can find all your groups on the same page. If you're signed in to an account managed by your work or school, the groups and features available depend on the settings for your organization.
*Standardized messaging—Topics are now called conversations and match Gmail patterns.
*Enhanced member management—The updated Members page provides quick access to group member subscriptions and permissions.

Free, but Google could just close it at any time.

I haven't used GG for years, though I'm still a member of several. You'd have to try it.

Not the same as the usenet inferface of GG.