Make sure to tell your references that you’re applying for jobs and have listed them as a reference to ensure you’re fresh in their minds when they get a call asking about you. Even better: Tell them what kinds of jobs you’re applying to, so they can highlight the skills you’ll need to get the job (it’s not a bad idea to send a copy of your current resume over as well).
Plus, you never know who your references know at the companies you’re applying to -- a quick reminder may get them to reach out on their own. We’ve hired interns because we’ve received glowing recommendations from their references before we even had a chance to call, and we've been hired because our references called in for us. A pre-emptive recommendation shows that the job candidate is so good, a busy person will go out on a limb for them.