Freebbble!

From the author: “This is a free set of eighty UI icons for personal and commercial use. Credit is appreciated, though not required.”

Free UI Vector Icon Set is a free Icon design resource made by Dribbble user Jonathan Hasson. As far as I can tell, its license is Free for Commercial and Personal Purposes.

Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.