The Noun Project aims to build a complete language with simple, clear, and concise visuals of common things.  Many of them are obvious and already in use in various signs and such, but several are more difficult.  For example, how does one visualize ‘Handle with Care’? Or distinguish ‘Car Rental’ from ‘Car’ ? It’s a tricky problem, and they have some clever solutions.

All of the visuals are available in vendor SVG format, and are freely available under a Creative Commons license.

NounProject.