The Stanford GraphBase

This book has two main goals. First, it provides dozens of examples of what
I like to call "literate programming" -- computer programs that aspire to be works of literature,
to be read and enjoyed by human beings although they ca also be read and
interpreted by machines.
[...]
Second, the programs in this book should be useful to anyone who develops methods
of combinatorial computing. Researchers who work on combinatorial algorithms need
standard sets of data for use in benchmark tests and
for comparison of competing approaches.