mansigandhi

My father has a non-profit org called Manthan (http://www.manthanindia.com/). They have a healthy amount of article sharing + discussion on their Facebook and Yahoo group. I'm looking to start off a segment for high schoolers, Manthan for Teenagers, and want to move that and the above to an independent discussion platform for various reasons.

What is a good (= easy, simple, clean) way to create a platform like HN? Are there existing solutions, possibly open source, that I could build off? Even a plug-in would work. I couldn't find anything myself.

Any help is appreciated!