Node.js
http://groups.google.com/group/nodejs<p>Ruby on Rails
http://groups.google.com/group/rubyonrails-talk<p>etc<p>What benefits or special features do Google Groups have? Posting via email?
If you ask around, you'll find that most of the people running Google Groups either hate or dislike Google Groups, however when their groups were first started it had a low-entry cost: it was free of charge and Google handled most of the annoyances of running a mailing list. New groups get added because it is still simpler than running your own mailing list.<p><a href="http://ejohn.org/blog/google-groups-is-dead/" rel="nofollow">http://ejohn.org/blog/google-groups-is-dead/</a><p>One should never underestimate the power of inertia.
They're free and they work reasonably well. They're not substantially better or worse than the other freely available mailing list services, in my experience. For projects that don't feel like running their own server and hosting a Mailman (or whatever) instance, they work fine.