Books

Algebraic Graph Theory - Home page for graduate level textbook "Algebraic Graph Theory" by Chris Godsil and Gordon Royle, published by Springer-Verlag, 2001.
cuscus.math.uwaterloo.ca/agt/

Digraphs: Theory, Algorithms and Applications - A comprehensive source of results, notions and open problems on directed graphs. Site offers the entire book for download as well as information on solved conjectures from the book.
www.cs.rhul.ac.uk/books/dbook/

Douglas West's Books - Home page of D. West with description of his books: Introduction to Graph Theory, Mathematical Thinking: Problem-Solving and Proofs, Combinatorics: A Core Course, The Art of Combinatorics.
www.math.uiuc.edu/~west/

Graph Theory - By Reinhard Diestel. Sites offers author and book information as well as a downloadable PDF version of the book.
www.math.uni-hamburg.de/home/diestel/books/graph.theory/

Graph Theory 1736-1936 - Two centuries of Graph Theory, by Norman L. Biggs, E. Keith Lloyd, and Robin J. Wilson.
www.oup-usa.org/toc/tc_0198539169.html