Have a flair for translation and want to help out an open source project in need? Consider helping the Symfony Project with their translation efforts for their manual.
The Symfony2 documentation is written in English and many people are involved in the translation process. First, become familiar with the markup language used by the documentation. Then, subscribe to the Symfony docs mailing-list, as collaboration happens there. Finally, find the master repository for the language you want to contribute for.
Full details on what they need help on and where/how to get involved are on the documentation page of the new Symfony 2 website.