After having gone through the process, about 2 years ago, of creating design standards for my current organisation (which in itself a whole different story), I love to see how other organisations handle this tricky area of standards. Putting aside the issues of stakeholder engagements, research, documentation, publishing of standards, acceptance of standards, governance…… Yahoo! has created a good Design Pattern Library covering many UI components, complete with a visual example and things to consider for accessibility.
I also like the way they have a separate UI Code Library for various design elements. The UI Library provides coding examples, which links in closely to the Design Pattern Library. Although the UI Library does not yet contain all the code related to the Design Pattern Library, it is still a very good support mechanism.