Documentation is a great place to get started. That is exactly where I started. When I wanted to learn more about jQuery and also help out, I started documenting and ended up writing many of the example demos that are now in the wiki while learning quite a bit about how jQuery worked. Just copy an existing APIExample section and modify it. As Jörn said, you can preview what will be up there and cancel if you don't like it. There is even a tutorial section that has some how- tos here http://docs.jquery.com/Tutorials
Yes there is a concerted effort to get the documentation in other forms (like the api browser) back in line with the version. But in the end the wiki is the documentation. All forms of documentation will only be as good as our community can make it. David