IcoMoon provides a package of vector icons, along with a free HTML5 app for making custom icon fonts. Browse among thousands of pixel perfect icons or import your own vectors.
BEM gives useful patterns and methodological recommendations on writing CSS, JavaScript, templates (and other web-related techs) in an extra-semantic way.
DOM Monster is a cross-platform, cross-browser bookmarklet that will analyze the DOM & other features of the page you're on, and give you its bill of health.