B001B1FDM2 Groundswell: Winning in a World Transformed by Social Technologies  ~ Charlene Li
0307409503 The Power of Social Networking: Using the Whuffie Factor to Build Your Business  ~ Tara Hunt
B002MZUPS8 Trust Agents: Using the Web to Build Influence, Improve Reputation, and Earn Trust  ~ Julien Smith
1591841933 Wikinomics: How Mass Collaboration Changes Everything  ~ Anthony D. Williams
1416595244 Why We Buy: The Science of Shopping--Updated and Revised for the Internet, the Global Consumer, and Beyond  ~ Paco Underhill

I would love to hear from you about any books that I missed in this list.