Learning a trade or skill that is unique to a lesser group of people is a great way to make sure your always one step ahead of the game. Polish off your Microsoft Office skills, brush up on your Spanish, or learn some html code. Anything which puts you one step ahead of another person in your field of employment makes you that much more desirable.
People who don't know advanced computer skills are often weeded out of many job opportunities in what is now a very technological age. Someone who is well versed in art may have a better experience in the culinary field. In your spare time, just take a few moments to learn something useful that just might help you make some more money in the future. Consider it an investment in life.