Because of disagreements with the W3C over copyright and Process I started working on web standards within the WHATWG, which has a fairly straightforward process and allows publishing under CC0 (public domain in countries that have that).
To make the specifications more hackable, they are now hosted at GitHub under /whatwg. Pull requests are welcome! whatwg.org/specs/ has an overview of the specifications developed. And the specifications themselves list how you can contribute via email and Bugzilla, or follow along on Twitter.
If you have the time to work on something, be sure to let us know! There is a Specs todo WHATWG Wiki page with some suggestions, but it is certainly not exhaustive.