[ame=http://www.amazon.com/Nonviolent-Communication-Language-Marshall-Rosenberg/dp/1892005034/ref=sr_1_1?ie=UTF8&s=books&qid=1292269276&sr=1-1]Nonviolent Communication: A Language of Life[/ame] by Marshall B. Rosenberg.
It taught me to see the world and the human journey in a whole new way that has absolutely improved my experience of being in relationship with my own person and others.
cheers,
Ian