Because you can never have too many open encyclopedia-type-thingies, Google has launched Google Doctype, a “Google-sponsored open encyclopedia and reference library for developers of web applications. By web developers, for web developers.” It’s set up to use an open license (Creative Commons Attribution 3.0 Unported License) and, unlike other similar resources, is explicitly set up to include code for testing and browser-compatibility tables generated by running that code against different browsers. Simple, direct… what’s not to like?
Disclaimer: I am neither a robot nor a librarian