Hi
Paul is right
try: http://domain.com/content/new
the file is: /design/standard/templates/content/newcontent.tpl
but this code produces all content since last visit (new articles, forum messages, etc.) You have to modify this file to get only forum topics.
Also, it will not display any content unless you are logged in. As the anonymous user, it would be since the last time any anonymous user viewed content on the site, which is usually only a few minutes ago.
This is a pretty neat feature, and never knew that was there.