"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." [via migurski]
People share and vote for their favorite command-line snippets at this site, and these are the most popular. Didn't know about "sudo !!"—that's worth the price of admission right there.