Free icons that are 100% GPL can be hard to come by. That’s why Automattic released Genericons, a set of icons that are 100% free to use. Genericons are vector icons embedded in a webfont designed to be clean and simple keeping with a generic aesthetic.”
Download iconsThese icons could be really useful for designers running on Twitter Bootstrap or even just integrating them into your site in general.
Keeping in line with the push that Matt Mullenweg made for retina across WordPress, these icons are no doubt, HiDPI icons.