Very useful book: "LaTeX Graphics Companion, The (2nd Edition) (Tools and Techniques for Computer Typesetting)"

The authors have done a great job at creating a virtual encyclopedia that documents packages for generating graphics. (Amazon link)

I am using LaTex for most of my writing projects and this book provided me with a fast start for generating UML diagrams, 2D and 3D graphics, formulas, Chess/Go/Backgammon boards and move lists, a very wide range of engineering diagrams, music scores, etc., etc. This is a large book (almost 1000 pages) but the layout and well organized examples from the book (which are easy to try out) make the whole book feel accessible and lots of fun to work with.