Here at Analytics for Joomla we love social media. We don't just track social media buttons with Woopra and have over 1600 followers on our Twitter account. Like social media, we love social components to enhance Joomla websites. The biggest (and best) community component for Joomla must be JomSocial.
This extremely flexible and userfriendly platform can turn a normal Joomla website into an amazing community where people can share content, interact and come together. JomSocial has just released a brand new version of their platform, allowing you to integrate their system into Joomla 1.6 websites.