I just came across the symbol signs created by the AIGA for the U.S. DAT. I'm sure everyone knows about these already, but if not, you can view them and download them for free. Here is a brief description on the symbol signs taken from the AIGA website.

This system of 50 symbol signs was designed for use at the crossroads of modern life: in airports and other transportation hubs and at large international events. Produced through a collaboration between the AIGA and the U.S. Department of Transportation, they are an example of how public-minded designers can address a universal communication need.

Labels: AIGA, Icons, Signs, Symbols