Seth Godin: Purple Cow: Transform Your Business by Being Remarkable
Excellent book for any business trying to figure out how to get ahead. This might be Seth's most successful (remarkable?) idea. A must read.

Seth Godin: Unleashing the Ideavirus
This is the book that made me fall in love with Seth and his ways. I wrote my own little book of notes while reading it.

Ben McConnell and Jackie Huba: Creating Customer Evangelists: How Loyal Customers Become a Volunteer Sales Force
My favorite business book ever.

Guy Kawasaki: The Art of the Start : The Time-Tested, Battle-Hardened Guide for Anyone Starting Anything
This book blew me away. Excellent resource for entrepreneuers, or would-be entrepreneuers.

Malcolm Gladwell: The Tipping Point: How Little Things Can Make a Big Difference
Every bit as good as the hype. Fascinating read about how ideas spread and how you can best spread yours.

Tom Peters: Re-imagine!
This is not a book for wimps. I still haven't taken it all in. It's densely packed with jewels, nuggets and mind blowing material. Feels like reading an encyclopedia that you can't live without.

Seth Godin: All Marketers Are Liars : The Power of Telling Authentic Stories in a Low-Trust World
Another great book from Seth. This one got me thinking about how I present my business, and how others want to perceive me. It gave me some great ideas. The "liar" metaphor was too much of a stretch IMO (it was done to grab attention but he had to spend too much time saying "no, not really liars") but the counsel is rock solid.