On the Symfony blog there's a post from Ryan Weaver about an upcoming event the project is hosting and how you can help - the Symfony Docs Hack Day (on March 30th).

The first commit to the Symfony documentation was over 3 years ago, and since then, we've grown to include a full book, lots of cookbook entries, and sections for most of the individual components. [...] But as we grow, we want to stay aggressive and continue to improve the quality of the docs. This means ensuring that code examples are accurate and pages are easy to understand, balancing the info you need with excess technical clutter. [...] And this is where we need your help! Whether you're a seasoned-Symfony veteran, a beginner, or even if you don't think your English is very good, we'd like you to join us on March 30th for our first ever Symfony Docs Hack Day.

The event is a virtual one - everyone will meet up on the Freenode IRC network in the #symfony-docs channel on March 30th from 9am through 5pm Central EU time. Everyone's invited, not just those who are experts in the framework. Documentation updates are a great way to learn more about a framework too! If you're interested in what kind of updates they're looking for, check out this list of open issues with the docs on Github.