1-First, this video from CBS News (7:17) marks the 100th anniversary of the fire.
2-This video (5:44) from WNYC tells the story through the recollection of a New York City resident whose grandmother and two aunts were among the victims.
3-PBS produced a feature on the fire as part of its American Experience series. This link is to the online printed materials it produced for further reading.
4-Cornell University's Industrial Relations School has a comprehensive site called Remembering the 1911 Triangle Factory Fire. In a carefully curated site, it tells the fire's story and gives information about each of the 146 victims. It has a full set of primary sources, including contemporaneous letters and newspaper articles and trial transcripts.
5-The U.S. Department of Labor's Occupational Safety and Health Administration (the federal agency responsible for workplace safety today) also has a terrific set of resources.
6-The AFL-CIO has an essay on the fire that puts the tragedy in the context of a rising national labor union movement.
7-Lastly, this feature from Time Magazine tells the story through 9 photographs with explanatory captions. Warning: Some of the images of the victims are graphic and disturbing.