SharePoint add-on for internal forum?

I’d like to ask the State webmaster community if anyone is using an add-on for internal use of SharePoint that creates the look, feel, and functionality of an internet forum?

The reason I ask is to find an add-on that has some traction in State use which my group can propose to our DWR Governance Board for adoption.

My team sees that an internal internet forum can be a great tool for passing knowledge and information around our organization to make work more efficient.

However, since our Department has already adopted SharePoint, we want to propose a tool that can integrate with it rather than a stand-alone tool.

By internet forum, I mean one that has the following common features and similar to the images below:

1) A top-level index of topics or subject categories
2) Use of sticky topics
3) Rating system for answers
4) Index of threads within topics
5) Expanded view of a thread with posted replies