Bookmarking and QA/Forum theme

I need a Question Answers/Forum theme for my site Top Ad Networks. I have one existing theme and want add this functionality. Please help is there any solution?

I also want one Social bookmarking theme like reddit. Suggest plz…

There’re some paid plugins/themes at ThemeForest/CodeCanyon but also some available at WordPress.Org for free.
You just need to search it to find the one you like