I only learnt today about OpenSocial, well.. never too late. It was announced at the Google BootCamp.
In a few words OpenSocial is basically Google's answer to social networking sites such as FaceBook, Hi5, Linked-in or MySpace. But it is not a Google product release, it's Google redefining the way these sites should interact with each other. Using OpenSocial, developers will be able to build fast applications to exchange information between each other using standards OpenSocial APIs instead of using each site's individual API.
I would compare OpenSocial a bit like Mashups and Gadgets using Microsoft PopFy but this time .. it's t use everywhere.
Of course FaceBook and MySpace are not yet partners of OpenSocial.. why not! ?;-)
OpenSocial - Google Code