A recruiter w/Professional Internships calls you to give you an offer.
After my final round interview, they said they'd call me in a week...well, stuff happens, and they didn't. So a day after a week had passed, I called the hiring mgr just to make sure because I wasn't sure if they'd call to let me know I DIDN'T get the internship. The next day the recruiter called w/an offer
Don't be afraid to call and check up on things to show them you are really interested, then again--don't call more than once.