Icons for your apps

Hi Guys,
Recently someone asked where it would be possible to find buttons and icons to be used in projects. With the contribution of a few people, including me, we gathered the following list:
Free for commercial (no link back needed):
Hope that this helps in your projects and if you know more places to get icons please share!
Rúben Gonçalves
Let me add these ones...

«Fugue Icons» available at http://p.yusukekamiyamane.com/ (link back required)

This is also a great source of free (no link back needed) simple icons, easy to adapt to any situation:

http://iconmonstr.com/ - Free simple icons for your next project


C. Alfaro
Icon fonts available here.
Here is my suggestion http://icons8.com/  free (link back needed)


And my contribution:

Terms of Use

These icon sets are licensed under a Creative Commons Attribution 3.0 License. This means you can freely use these icons for any purpose, private and commercial, including online services, templates, themes and software. However, you should include a link to this page in your credits. The icons may not be resold, sub-licensed, rented, transferred or otherwise made available for use. Please link to this page on fatcow.com if you would like to spread the word.

A great thing about this library is that it includes 16x16 and 32x32 icon sizes.