I wish I had learned C++, personally. A number of the places I was hoping to work for required many years experience in it. Like or hate the language, it's used frequently. Or at least it was.
Some other things I wish I had done/learned:
* working with external libraries in C
* working in groups on LARGE projects
Something I did learn through extracurricular activities, not school work for the most part:
* SOLVING PROBLEMS!!! UVa, TopCoder, Google Code Jam, ACM Programming Contest. Learn how to take a given problem and convert it into code.
Some other things I wish I had done/learned: * working with external libraries in C * working in groups on LARGE projects
Something I did learn through extracurricular activities, not school work for the most part: * SOLVING PROBLEMS!!! UVa, TopCoder, Google Code Jam, ACM Programming Contest. Learn how to take a given problem and convert it into code.