Often new version announcements (like the one Greg just sent) are cross posted to related groups. The traffic is not heavy and the service useful.
As for ongoing discussions (good idea!), I would  suggest http://www.python.org/community/lists/ from which I quote:

To request a new list, send e-mail to postmaster @ python.org
 
 That's where the pywin32 group lives, and it works rather well.
--
Vernon Cole

On Mon, Nov 16, 2009 at 3:31 PM, Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:
>
> John Finlay wrote:
>
>> Start your own list for the community that is interested in your project.
>
> That's not going to reach anyone who doesn't already
> know about it.
>
> It's probably a good idea for ongoing discussion,
> though. Any suggestions on the best way of going
> about it? I could start a Google Group, but I'd
> prefer a real mailing list server if possible.
>
> --
> Greg
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