One thing that is particularly useful for question/answer type forums
(ala the Ruby forum and the Rails forum) is to have a 1 click search
that gives you all topics that haven’t been responded to yet. This
would allow those of us who are on the forums specifically to offer help
to quickly identify those people who haven’t recieved a response yet.
And “advanced” version of this would be a search that gave all topics
that didn’t have someone other than the author respond. There have been
a few occassions in the past where I would respond to my own message (to
clarify an issue, offer additional info, etc) and I never got a
response, even though the post count is > 1 
This might make a good module in the plugin system that I haven’t
touched in quite some time 
-Matt