Processing A Programming Handbook for Visual Designers and Artists by John Maeda
Processing: Creative Coding & Computational Art: Creative Coding and Computational Art (Foundation) by Ira Greenberg
Making Things Talk: Practical Methods for Connecting Physical Objects by Tom Igoe
Creative Code: Aesthetics and Computation by John Maeda
Physical Computing: Sensing and Controlling the Physical World with Computers by Tom Igoe
Physical Computing: Sensing and Controlling the Physical World with Computers by Tom Igoe
This next one looks like a good place to start.

Programming Interactivity: Unlock the Power of Arduino, Processing, and OpenFrameworks by Joshua Noble
Im sure this list will grow...
And here it grows:(6/5/2010)

Learning Processing: A beginners guide to programming Images, Animation and interaction by Daniel Shiffman
Note: Look into Arduino
Book:
Getting Started with Arduino by Massimo Banzi