400 Free Png Icons at 32px for Web and User Interface Designers.
Pyconic Icons FREE are released under the Creative Commons Attribution 3.0 Unported (CC BY 3.0).
These icons can be used both commercially and for personal use, but you must always add a link to http://www.pyconic.com in a prominent place (e.g. the footer of a website), include the CC-BY license and the reference to http://www.pyconic.com on every page using Pyconic Icons.
If you use the icons as a part of your design in your product it is perfectly fine. Keep in mind, please, that it is not allowed to resell the icons themselves, the icons as such are the property of the author.
All logos and trademarks in social icons are the property of the respective trademark owners.®