Alon/Spencer, The Probabilistic Method (2e)
Anderson, Combinatorics of Finite Sets
Brualdi, Introductory Combinatorics
Cameron, Combinatorics: Topics, Techniques, Algorithms
Chartrand/Lesniak, Graphs and Digraphs
Graham/Knuth/Patashnik, Concrete Mathematics
Graham/Rothschild/Spencer, Ramsey Theory
Stanley, Enumerative Combinatorics
Tucker, Applied Combinatorics
Trotter, Combinatorics and Partially Ordered Sets
vanLint/Wilson, A Course in Combinatorics
Welsh, Matroid Theory
West, Introduction to Graph Theory