Arduino book recommendation
I've found Arduino Cookbook from O'Reilly to be nice. There are also a ton of tutorials on the Web, and of course the examples that come with the dev environment.


  The recipes in this book provide solutions for most common problems
  and questions Arduino users have, including everything from
  programming fundamentals to working with sensors, motors, lights, and
  sound, or communicating over wired and wireless networks. You'll find
  the examples and advice you need to begin, expand, and enhance your
  projects right away.
  
  
  Get to know the Arduino development environment 
  Understand the core elements of the Arduino programming language
  Use common output devices for light, motion, and sound
  Interact with almost any device that has a remote control
  Learn techniques for handling time delays and time measurement
  Use simple ways to transfer digital information from sensors to the Arduino device
  Create complex projects that incorporate shields and external modules
  Use and modify existing Arduino libraries, and learn how to create your own