FlatIcon

Tons of modern CC-BY icons! Search by keyword, and then choose the file type (.png, .psd, .svg, .eps) and the size. An incredible collection that will cover most of your icon needs.

http://www.flaticon.com/

“Flaticon offers users, high quality graphic designs: totally editable vectors carefully selected by our design team in order to provide our users with great content that can be used in both personal and commercial projects.”