A cool way to say you don't do anything important. During a conversation, when a person asks the other what they do, and that other person does't really do anything, they don't want to say they do nothing and not appear interesting to the other individual. By saying they DJ on the weekends, it makes them seem interesting and more fun to hang out with.
People add this phrase under hobbies for their myspace/facebook pages to seem interesting.
John: I DJ on the weekends.
Dave: Really? That's awesome!