Are there any plugins/add ons for the forum mod?

The only ones I am aware of are our own extensions that the EllisLab team have written for our own needs.

Are you looking for any specific features?

I think one reason there aren’t many extras is that there haven’t been many requests. In my situation I build plugins/extensions/modules as needed for myself or my clients. I have created only one forum module/extension because only one client has needed one. The only thing keeping me from releasing it is that it started to show some performance problems recently. I made some changes and I want to observe them for a while to see how they hold up.