Get out and enjoy all that Boston has to offer! Spend the summers here -- Boston is beautiful in the summer. Get a guidebook and peruse it. Read the Phoenix/Weekly Dig/Improper Bostonian to know what's going on. Go picnic on the Boston Harbor Islands (there are fast ferries to Spectacle and Georges), get a bicycle and take it everywhere (Boston is a bike-friendly town despite its reputation for crazy drivers, mostly because everything is so close together), learn to sail on the Charles River, ride the Minuteman trail, do the corn maze in the fall at Davis Mega Maze, go skinny-dipping (or normal-dipping) in Walden Pond, walk the Freedom Trail and Newbury Street, volunteer at a high school, relax at Tosci's, go to weird plays (at Mary O'Malley park in Chelsea there are free plays in the summer, plus Back Bay and in the theater district), join ubernerd clubs like the Amateur Telescope Makers of Boston, acquire the local passion for the Red Sox, attend the film festivals and movies at the Somerville theater or the Brattle or Coolidge Corner or the Landmark or Harvard or MIT, go camp out at 9 a.m. on July 4th for a spot on the Esplanade to picnic and watch the Boston Pops concert and fireworks over the river with 500,000 other people.
To be honest, most of the cool stuff I love about Boston I didn't discover until I had been here for like five years and started venturing more off the campus.