If you're already in Boston and you have a car, you can take Storrow Drive and get off at Massachusetts Ave. After you cross Harvard Bridge, you'll be in Cambridge and at MIT.
Driving in Boston is insane, especially with the big dig and all kinds of nonsense constructions projects going on. Don't bother with a rental car, you can take the T (subway) from Logan into the city, and the bus system is pretty good too.
You can get here by taking the subway from Logan airport or you can drive. But if you want to arrive in style, have a boat drop you off at the Harvard Boat House on the Charles River.
By car, bus or by the 'T' and personally I would take the T.
Finally ... a view of Cambridge and M.I.T. from the Harvard Bridge in Boston. Walked over on my lunch hour.
MBTA, bus, car or walk.