I know you said you're not really into seeing art-stuff, but you should at least consider stopping by the ICA on our Waterfront.
Shepard Fairey has his big exhibition showing. It's an awesome [new/modern] building, and the area is nice.
Be sure to check out the North End (Boston's "Little Italy"), and the historic sites in the immediate "Downtown" area: Faneuil Hall, the Boston Massacre Site, our State House, the Common and Public Gardens. Also noteworthy is the Paul Revere House, and the U.S.S. Constitution (in the Charlestown Navy Yard). Following the
Freedom Trail would take you by most of all these sites. We also have the "Harborwalk" that follows, well, the Harbor/Waterfront.
And of course, for shopping, you'll have to stroll down
Newbury Street in the Back Bay, but be prepared to pony up the cash! Despite all the high-end boutiques, there are more affordable destinations on the same street, including H&M.
Boston has plenty of great destinations for food. Some of my favorites include Fire and Ice, Victoria's Diner, South Street Diner, Top of the Hub, Beacon Hill Bistro, the original Pizzeria Regina, Rendezvous and
Ten Tables. There are couple
Tealux's around, and Expresso Royale, or the 1369 Coffeehouse for desserts and coffee.
Also, you could spend hours at Harvard Square alone. One of my favorite places in Cambridge is Central Market, a 24 hour market/food stop. But food aside, there's good shopping and sight-seeing in that general area.
The Coop is the MIT bookstore, which you mind as well see if you're there. The Red Line (outbound to Alwife) will get you to Cambridge from Boston proper.
Make sure you get a CharlieCard MBTA pass, as the $2 per subway/trolly/bus ride adds up fast.
