How do I see who's online to my linked Gchat and Facebook Chat in Messages? I had Google Chat and Facebook Chat linked to iChat, but since I upgraded to Mountain Lion I can't see who's online through the bar that used to display along side messaging window. Any ideas?
The sidebar shows your list of open chats. When someone is offline, the text "Offline" shows under their name:



This also depends on whether you have iMessage-enabled contact information for those people — it seems that if you do, they never appear as Offline.

(Also note that the buddy list window still works well for seeing who's online!)