I am going to Boston in October and I was hoping to stay in a bed and breakfast with anold world ambiance. I don't even mind a bathroom down the hall, if the mood (and the price) is right. Location is important, but I'm willing to sacrifice in travel time what I gain in charm.
Does anybody have any suggestions?

Three favorites: Newbury House on Newbury St. in Boston -- convenient to all; IrvingHouse on Irving St. in Cambridge -- a few blocks away for Harvard Sq., which makes it convenient to the T ; and the John Jeffries -- closer to an actual hotel but still sort of quirky/boutique-y (breakfast is not much more than a buffet) and VERY convenient to/on Beacon Hill. All 3 have websites.

Thank you -- I am also looking at prices I only need a single.

Old world charm with small wallet?

I've also heard good things about the Kendall Square Hotel in Cambridge, which is bigger than a B&B but still charming--quilts on the beds, etc. The hotel consists of a renovated fire station and a newly built annex--the rooms in the fire station are more quaint. Big plus is it's right in Kendall Sq. where there is a T stop.

Another option is the Harding House in Cambridge which is also operated by the same folks who run the Irving House.

I second the rec. for Newbury House--good location but maybe a bit nosiy during the day since Newbury St. is a very popular outdoor shopping area.

We loved the Newbury House when we were there after a family wedding, with guests from England. Great location for exploring Boston, nice breakfast, comfortable room. And even a place to park, which is a real find in that neighborhood!