Q&A Plugin?

Is there some sort of plugin where I can host a number of questions and answers, independently of any posts?

For example, the plugin would allow me to enter questions and answers in a form, and possibly display top/recent questions and their answers somewhere…maybe in the sidebar or something.

Maybe it also has a form where people can enter their questions, and where I can review + answer questions!

…or maybe I should just have a Q&A tag/category…