Learn to cook. If you can cook for yourself, you'll eat healthier and better and save money. Also you can impress your dates.
I concur. It surprises me every one in a while at the number of people who cannot cook. Given that we require nourishment 3 times a day, daily, for the rest of our lives (assuming that we die), it seems obvious that cooking has an extremely high return on investment as compared to many other skills that people suggest we pick up, such as learning an instrument or learning a sport.
This September I'll start college aiming for a computer science degree, and I want to use the summer for self-improvement. I'm very uncertain about what skills I should try to learn, though, and recommendations would help.