My two options so far are Dolphin from Boonex (has a free option supported by advertising) and OpenWack/Oxwall, an open-source platform.
Somehow though, I can't help feeling that I'm missing something from the picture.
I'd be extremely grateful if any of the seasoned warriors could share their experience and advice.
By the way, if the situation warrants it, I wouldn't mind coughing up a few dollars for a license. Still, for obvious reasons, I would prefer a free platform.