Google OpenSocial launches today and it looks very promising, especially for developers of social net applications. http://www.techcrunch.com/2007/10/30/details-revealed-google-opensocial-to-be-common-apis-for-building-social-apps/ OpenSocial is a set of three common APIs, defined by Google with input from partners, that allow developers to access core functions and information at social networks: * Profile Information (user data) * Friends Information (social graph) * Activities (things that happen, News Feed type stuff) They are already partnering with networks Friendster, Myspace, Hi5, and Orkut and developers RockYou and Slide.
OpenSocial is an API. Not that useful unless your site is a social network. EDIT: The above post was edited...