The Massachusetts 9/11 Fund, greatly assisted by a grant from the United States Department of Agriculture's Living Memorial Project, dedicated a very special feature in the Boston Public Garden on July 12, 2004 to memorialize the victims of September 11, 2001 from Massachusetts and New England. You can read about the origins of this memorial here.
You can read about the architectural design features of the memorial here and also listen to an audio description of the memorial here. A brief film tour [not narrated] of the memorial can be found here. You can find a walking tour of the Boston Public Garden here, featuring the memorial as the third stop on the tour.