OpenSocial is a platform for multiple social networks where you are able to place different small web applications on peoples pages.

This will change how social networks grow and change as it will allow people from different social networks to interact and do things together.
There are a few main social networks using OpenSocial go to the partners page to check them out.

It is based on similar code to Google gadgets. Using a set of javascript libraries to access a persons details, social network and activities.

The use of JavaScript, HTML and XML allows developers to easily develop apps for the different sites compatible with OpenSocial.
Google is even offering hosting for the different gadgets or you can host them on your own server. I can't wait to see this take off I really hope it takes of better than OpenID that is another thing I hope Google get behind so that it can become a standard.

http://code.google.com/apis/opensocial/

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Andrew
Web Designer/Programmer