Make Your Own PCBs with EAGLE: From Schematic Designs to Finished Boards
Note: Working with breadboards or Prototyping PCB boards can be tedious and with cheap manufacturing in China, it makes sense to learn enough about EAGLE to make your own boards.
Absolute Beginner's Guide to C
Note: C hasn't changed much and the Arduino uses a limited subset of it so any copy of this book will be handy. Ignore the price listed. You can get a used copy for under $10.