I was in Boston years ago, and really enjoyed touring the Statehouse.
Also, while I enjoy walking tours, if the weather’s bad, there’s the option of a guided tour on a bus - not as intimate as a walking tour, but more comfortable on a rainy day.
On visiting the Constitution:
Right now the ship itself is undergoing renovations, and is kind of in sad shape. Just about all of the masts and rigging have been taken down, and there’s a temporary cover over the whole ship while they replace the upper deck. Still, it’s probably worth seeing if you manage to get there when it’s not as busy (though school groups show up intermittently during the morning and afternoon). The museum is also pretty good, but not particularly huge.
Getting there, IMO, is easier than some of the posters have led you to believe. It’s a 10-15 minute walk from North Station, and also there’s a certain shuttle bus you can take. It’s not intended for tourists, but nobody minds as long as you don’t try to squeeze on during rush hour. PM me if you’re interested, and I’ll pass along the details.
Thanks everyone for your suggestions. I’m leaving for Boston tomorrow and will probably be quite busy until the weekend. Saturday and Sunday, however, I should be free. If anyone is interested in meeting up (for a pint, perhaps), I’ll be happy to as well.