CSS Lint : CSS Lint points out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problemati...
csscss : csscss will parse any CSS files you give it and let you know which rulesets have duplicated declarations.
* { CSS:resetr } : To help you find the perfect CSS-reset styles, CSSresetr lets you try all the best CSS Resets on a variety of web pages – even your own.
UnCSS : UnCSS is a tool that removes unused CSS from your stylesheets. It works across multiple files and supports Javascript-injected CSS.