eXo Platform 3.5 provides many extension points and API for developers, allowing them to create very cool stuff.
I have developed a small extension that allows any user to associate his Twitter account to his eXo Platform account. This extension simply post on your Twitter account when you write a message with a special hashtag (#tw).
This is a very quick development that I have done while waiting for my kids, so I still have things to integrate to provide complete feature, but this is a good example to show how you can extend the platform.
You can view it in action in this video:
You can download the source code and the binaries from this GitHub project. I hope to find some time to complete the feature, and document this use case.