OR-Library is a collection of test data sets for a variety of OR problems.
A full list of the test data sets available in OR-Library can be found here.
There are currently 27 data files.
These test problems are taken from J.E.Beasley "Linear programming on Cray supercomputers" Journal of the Operational Research Society 41 (1990) 133-139.
The problems in Table 1 of the above paper are based on the LP relaxation of a set of test problems for the set covering problem given by Balas and Ho. See the file scpinfo for details of how to obtain these problems (15 data files in total).
The problems in Tables 2 and 3 of the above paper are based on the LP relaxation of a set of test problems for the assignment problem. See the file assigninfo for details of how to obtain these problems (12 data files in total).
The values of the optimal solutions for these test problems can be found in the files lpopt and assignopt.
Click here to access these files
OTHER SOURCES
Linear programming problems can also be obtained from NETLIB
A variety of linear programming problems are also available here