They are building a global visual language that everyone can
understand and in addition to downloading icons as a service you can also upload ones you design and contribute to this growing visual language. The Noun Project also organizes Iconathon, design workshops around the US that help to identify and design icons or symbols for various organitions or civic pursuits. I'm bummed that I'm only getting my head out of the sand now and missed their Iconathon in Los Angeles last summer focusing on the LA River.
I ❤ The Noun Project.