Sorry for such a brazen bragging, but, being a co-moderator of a history discussion board, I would like to add one more name to the list you have posted: Sima Qian Studio (http://www.simaqianstudio.com). It is not confined to the antiquity, but, at least, our Ancient History subforum
(http://www.simaqianstudio.com/forum/index.php?showforum=8) is active enough.