Graph Theory eBook
Here is a complete text on Graph Theory freely available on-line:
This appears to be a college- or graduate-level text, and it covers the basic ideas from Graphs and Trees to Colorings and Networks.
Each chapter is available as a separate PDF and contains numerous exercises. There are a number of appendices, like this one discussing Some Interesting Graphs, as well as a glossary and index.
I wish my own professor had used this, rather than making us all spend $100 on a flimsy paperback textbook!