A couple companies that come to mind who have been doing this awhile (I know people who have used them for years) are Online Institute (OLI) and Parachat.
OLI allows picture posting, linking, video embedding, private messages and has full membership controls (like a forum). check out:
free demo is here:
parachat has many of the same features and allows large rooms and supports "event chats" -- see:
watch out for the "free" chats, a friend tried one and the server was sloooowww... these two are at least low cost and have good support
hope this helps