Metro is a design style and language developed by Microsoft. Products like Zune, Windows Phone, Xbox and the soon to be released Windows 8 follow the Metro design style.   http://www.blinkux.com/metro/principles.html

Nice little overview of practical style guides   https://gimmebar.com/collection/4ecd439c2f0aaad734000022/front-end-styleguides

Handy, rebrandable ExpressionEngine client guide, second edition   http://headspacedesign.ca/blog/entry/the-expressionengine-2-client-guide-is-here/