We have a mailing list for pgSphere users and developers at Google Groups. You can read the mailing list archive on-line, but you need to become a member of the mailing list if you want to post messages.
To join the mailing list, write an e-mail message (subject line and contents do not matter) to firstname.lastname@example.org. Shortly after that, you will get an e-mail message such as "Join request for pgSphere users and developers ...". Just reply to that e-mail without adding anything. That should be all. (Generally, do not use the URL provided in this "join request" message, as it will only work if you are currently logged into a Google account.)