This is one I remember using that I didn't see on there:

Professors William T. Trotter [1] and Mitchel T. Keller [2] Applied Combinatorics [3,4]

[1] http://people.math.gatech.edu/~trotter/

[2] http://rellek.net/home/

[3] http://rellek.net/book/app-comb.html

[4] https://people.math.gatech.edu/~trotter/book.pdf