Suggest a plugin for up/down voting posts [closed]

I need a free wordpress plugin that will allow the users to upvote or down vote every post. Something similar to stackoverflow.com

If not give me suggestions of how to create one. I am a java programmer and have never coded anything in PHP.

For all of my rating uses i use WP-PostRatings

http://wordpress.org/extend/plugins/wp-postratings/