I believe the museum of science is still showing their star wars exhibit there. Check www.mos.org and see if there are any tickets available when you're here. If you go, make sure you go to the Cheesecake Factory next door in the Cambridge Side Galleria Mall. Excellent food.
I went to the exhibit when it first started. It's good, not great, but good. I really wish they had more lightsaber props but they only had like 4 I believe. Though the highlights for me was the millenium falcon and the tantive iv models.
You HAVE to go to the Museum of Science and see the Star Wars exhibit. Its great. Seeing the full sized landspeeder was worth it alone. That thing is unreal to see in person... I felt like a little kid the first time I saw it.
Also in the museum but not a part of the exhibit (in the general exhibit halls) is the full sized Naboo Starfighter and there's another original R2 in the electricity room.
Also, not so much a prop but the civil war relief sculpture at the end of the movie "Glory" is across the street from the State House on the edge of Boston Common.
There aren't many "prop" things to see in Boston but there are TONS of touristy-type, history things to see. I'd focus more on those if I were you.
I believe all of Good Will Hunting was filmed here, most of With Honors, Blown Away as well was filmed.
Definitely hit up Fanuel Hall. I recommend going to 2 restaurants and 1 bar, and 1 club in that area. McCormick and Schmicks and Durgin Park both have excellent seafood, Q Club is really good club, and of course the Purple Shamrock.