<p>I would like to create a private customized social networking for my company employees and partners so that they can collaborate, exchange messages, share experiences (events, book references, etc) and be grouped into communities. Does anybody know good Java framework for start developing this? </p>

<p>I would be looking for something that would contain basic components such as Profile, Friend List, Community, Events, Messages, etc. Each of this component could be extended to implement domain specific features. It would be nice if it also supports OpenSocial.</p>

Shindig is in incubation at Apache :
http://incubator.apache.org/projects/shindig.html
YouTube Link About Shindig :
http://www.youtube.com/watch?v=ZcWszaReqXI
A List of Open Source Social Networking >Applications< Written in Java:
http://www.manageability.org/blog/stuff/java-open-source-social-network