Our newsgroup is accessible via Google Groups as well, and you can post to alt.astrology.moderated if you have an account with Google.
https://groups.google.com/forum/#!forum/alt.astrology.moderated
LinkedIn has several forums for people interested in astrology. You can find those I am a member of at this link:
se.linkedin.com/in/kjellpettersson/
I recommend in particular OPA, Organization for Professional Astrology, though I believe it is open only to professional astrologers so if I remember that right one would need to qualify to be a member. LI itself probably has a real name-policy, but they seem to be lax with it.
Though not exactly a forum, and I am also not exactly myself that active there now, there is also quite a lot of astrological activity on Twitter. I follow primarily astrologers and people with a high quota of related content, so if that is also of interest you could check out those I follow:
https://twitter.com/kjellpettersson
(It is possible there is a direct link to a tab with only those I follow, but I cannot find it.)
Also not a forum, but still with some interesting content relating to astrology, is Quora (
quora.com). Cave canem, though, as there are a lot of quite hostile skeptics there. The site has a strict real name-policy.
Google Plus and Facebook also have groups of various kinds, too many to list here. I cannot right now find a way to list those I am a member but should there be interest contact me on the sites in question and I'll respond. (All my social media presences are available via my homepage,
kjellpettersson.com.) Both G+ and FB claim to have real name-policies, but they are not that strict with them it seems.
/K