The Revolution Hotel.

It's right downtown in a very nice area. It's within walking distance of South End, Back Bay, Downtown Crossing, Chinatown, etc. It's close to the train lines. It's about as good of a location as you can get.

It's relatively cheap because the rooms are about 115 sq ft and don't have bathrooms in the room. Instead, you have to walk down the hall to a shared wash room. The shared wash rooms are quite nice, and you get your own individual bathroom in the wash room (door that locks, toilet, sink, shower, towels, etc).