Actually, if you're exploring the city, you cannot overlook the bombing sites. The region around Boylston Street is very busy and crowded with media teams and tourists. There are several spots that serve as makeshift memorials for the victims of the attacks. People gather at these spots and you can easily feel their sadness and their sympathy for those who were killed or injured.
PS. After the bombings, there was a discussion in the media about which pictures could be shown and which should be held back. With a few exceptions, the newspapers ran only cropped versions of the most graphic images, and there were also cases of improper manipulation (see http://nppa.org/node/60892 for a discussion on the issues). For those of you who'd like to see a painfully realistic and detailed depiction of the devastation caused by the bombings, take a look at the image collection at http://cryptome.org/2013-info/04/boston-bombs/boston-bombs.htm. But be warned, the material is very graphic and hard to look at! Thanks to my friend for sending me the link.
