The Unclassified NewsBoard (short UNB) ist a great, fast and lightweight forums software which is very easy to extend and customize. I use it for many years now. UNB was the 1st board software with XMPP notifications for new replies in threads or users.

I have written now a small plugin which notifies board admins of new created threads. There is no need to poll the RSS feed every X minutes or hours anymore.

You can find the plugin here.