The Internet Archive (IA) and their wonderful Archive-It service is continuing to build and make searchable a collection of materials/news reports/social media about the Boston Marathon Bombing.
In Their Own Words:
This collection is comprised of contributions from curators and subject matter experts; and includes news articles, blogs, social media sites, and organizational websites related to the 2013 Boston Marathon Bombing and its after effects.
The Boston Marathon Bombing web archive is available here.
Finally, pages included in the archive are full text searchable (unlike pages made accessible via the IA’s Wayback Machine).
See Also: Other Web Archives that Focus on “Spontaneous Events”
103 collections are listed.
See Also: More Than 1900 Collections of Archived Web Content
These are public collections utilizing Archive-It.