normally community websites are built using a cms ,a good one is called drupal but you have to have a solid knowledges of xhtml css php and mysql to start playing with it.
there are a lot of books out there ,try to find a good one and read it.
Do create a community like that, you will need a huge programming background.
That link that you posted is hilarious though, I’ve never seen such a blatant rip of Facebook in my life. If Facebook ever finds that site, you can guarantee they’ll have a law suit on their hands pretty quickly if they don’t immediately take it down.