There's a link to list all active users on Daniweb from the forum nexus. It would be nice to also have that feature for each individual forum, or at least a way to sort by forum. Would that be too difficult to implement?
I think each sub-forum displays active members at the bottom of the forum ... but I do think that there should be an active member list for the whole forum category too like in tech talk or coffee house.
The best that I can do for you right now is make the # of users online in the sidebar hyperlink to the who's online page. I might go all out making the who's online page forum specific but most likely that won't happen until summer break in a month or so.
It works. It's live. It's forum specific. It operates the same way as the "today's posts" idea ... it handles subforums (i.e. if you click Who's Online in tech talk, it includes all of the subforums, but if you click in Viruses and Spyware, it's just Viruses 'n' Spyware that you see)