I was chatting with Jim King at lunch about John Backus and the Fortran compiler (Jim worked at IBM Research for many years). Jim used Fortran (II?) and Fortran Monitor System on an IBM 709 in college in the early 1960s, and had some interesting anecdotes (e.g., the compiler turned on a front panel indicator lamp once it determined there were no syntax errors, …) — I can see that getting oral histories of users/developers will be interesting.
Jim suggested IBM’s SHARE user group library as a potentially interesting source of material. (And perhaps there were similar user groups for a few of the other companies?) Also, he worked for Boeing in Seattle in the 1960s, and said they had an extensive 7090 program library, with detailed requirements for documentation. It could be another interesting source, although he doesn’t have any current contacts into Boeing.