Sedgewick R. Algorithms in C. Part 5. Graph Algorithms 3ed 2001

Textbook in PDF format

A complete overview of graph properties and types
Diagraphs and DAGs
Minimum spanning trees
Shortest paths
Network flows
Diagrams, sample C code, and detailed algorithm descriptions
The Web site for this book (http://www.cs.princeton.edu/~rs/) provides additional source code for programmers along with numerous support materials for educators