Font Awesome gives you scalable vector icons that can instantly be customized — size, color, drop shadow, and anything that can be done with the power of CSS.

One Font, 439 Icons, In a single collection, Font Awesome is a pictographic language of web-related actions.

Font Awesome is fully open source and is GPL friendly. You can use it for commercial projects, open source projects, or really just about whatever you want. Attribution is no longer required as of Font Awesome 3.0 but is much appreciated: "Font Awesome by Dave Gandy - http://fontawesome.io".