[Kipper is King]

The Boston Museum of Science is kinda neat, but it's more for kids. They have the World's Largest Van de Graf generator there, which is shockingly neat!

I second seeing the aquarium. That is great for anyone.
Also going on the previously mentioned duck boat tour is touristy fun, and it's in a beautiful park.

Lastly you gotta check out Walden Pond (beautiful, and read Henry David Thoreu's writing while you're there) and go out to Cape Cod if you have time. I found Marion to be quite nice.