Most are electronic collections specifically about the 9/11 attacks.
These digitized sources from the University Libraries' Archives and Special Collections capture the reactions of Ball State students in September 2001 to the attacks on the World Trade Center and Pentagon and the destruction of United Airlines Flight 93.
These items are part of the Digital Media Repository, a collection of digitized archival resources about the history of Ball State, Muncie, and Delaware County. It is a good place to search for more primary sources about the local reaction to the attacks.
These are broad electronic collections of primary sources. Use search terms to locate material about the 9/11 attacks.
These resources contain digital reproductions of historical newspaper and magazine articles. You can use them to find news coverage of the attacks and their aftermath.