Noizio - Feeling that the noise of the big city is too much for you to bear?
SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.
chatback - Automatically connect to people around you & chat
JomSocial - Open Source Social Networking Software. Award winning open source community software by JomSocial. This social networking software is widely used by many Joomla users.
THINK thenlive - Location-based social media
phpFox - phpFox is a powerful social network platform for niche communities