When I made my first site, I found it very hard finding 'high quality icons' for free. Therefore I came with this idea, why not give people the chance to download nice icons for free.
F. Stjernfelt. Proceedings of the 14th International Conference on Conceptual Structures (ICCS 2006), том 4068 из Lecture Notes in Computer Science, стр. 70-86. Springer, (2006)