Of the skills I learned in college, the most useful have been 1) spoken Mandarin and written Chinese; 2) data structures and algorithms (as many have noted); 3)

Of the skills I learned in college, the most useful have been 1) spoken Mandarin and written Chinese; 2) data structures and algorithms (as many have noted); 3) reading electronic schematics and digital timing diagrams; 4) proficiency in vi and emacs; 5) Unix utilities and shell scripting (if you'd told me in 1985 I'd still be using this 27 years later I would have been surprised).