The UCSD p-System Users Society (USUS) maintained a library of Pascal floppy disks containing source code and programs.
The group was described as “an international non-profit organization dedicated to promoting and influencing software standards to aid in the development of portable software.

Here the disk images for volumes 1 through 29 of the US library, and volumes 3 and 4 of the USUS UK collection, unpacked so the source files are readable.

Also the raw volumes of the USUS library are available

Contents of the library

Newsletters
USUS Newsletter V1N01 1980-08
USUS Newsletter V2N2 1987-12 (Winter 1987-1988)
USUS Newsletter V2N3 1988-03 (Spring-Summer 1988)
USUS Newsletter V2N4 1988-07
USUS Newsletter V2N5 1988-08
USUS Newsletter V2N6 1988-09_10
USUS Newsletter V2N7 1988-11
USUS Newsletter V2N8 1988-12
USUS Newsletter V3N5 1989-05_06
USUS Newsletter V3N6 1989-07_08
USUS Newsletter V4N2 1990-03_04
USUS Newsletter V4N3 1990-05_06
USUS Newsletter V4N4 1990-07_08
USUS Newsletter V4N5 1990-09_12
USUS Newsletter V5N1 1991-01_02
USUS Newsletter V5N3 1991-12