Sleek Social Media Icons
Thin lines, iOS 7-like.
Sleek Social Media Icons is a free Icon design resource made by Dribbble user Daniel Klopper. As far as I can tell, its license is Creative Commons Attribution-NoDerivs.
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.
