Start a karate club!
It's a great way to keep in practice and it looks great on your resume to be the founder/president of a club in college. You may be thinking that you won't have time or you won't be qualified to teach a karate class. You don't have to. A college karate club can be something as simple as a time/place where the various martial artists on campus can meet, practice, and if the rules of the college permit you can even have some sparring sessions. You're essentially inviting other martial artists to join your practice session.