More and more contributor groups are making the move to make.wordpress.org, with the Polyglots and Core groups recently being moved to .org, and the brand new Events group making an appearance. If you want to get involved with contributing to WordPress, make.wordpress.org is place to get started. The contributor groups currently living there are Core, Plugins, UI, Accessibility, Themes, Polyglots, Systems, and Events.
Only a few more to make the move: I’m looking forward to seeing the Codex team and support finding their own room in the make.WordPress.org home.
If you want to learn more about contributing to WordPress, check out the page on the Codex.