Great: a free online version of Diestel's Graph Theory book
I noticed this on reddit: Springer-Veralag has a free online version of Reinhard Diestel's "Graph Theory" book. I usually use the Corman/Leiserson/Rivest "Algorithms" book, but they only have 200 pages on graph theory. This book is in the Graduate Texts in Mathematics series but the math is fairly easy to follow. Useful resource.