Short List for Life

Motivation:
Think and Grow Rich - Napoleon Hill

Motivational Speakers:
Zig Ziglar - anything just watch him in YouTube.

Interpersonal relations:
How to Win Friends and Influence People - Dale Carnegie

Leadership:
The 21 Irrefutable Laws of Leadership - Maxwell

Money in general:
Rich Dad Poor Dad - Robert Kiyosaki

Investing:
The Intelligent Investor - Benjamin Graham

Self-help/Motivation/NLP:
The Greatest Salesman in the World - Og Mandino

Thinking out of the Box:
How to Fail at Almost Everything and Still Win Big - Scott Adams

Lifestyle management:
The Four Hour Work Week - Tim Ferris

Marketing:
Seth Godin - see his blog or any one of his books and changethis.com manifestos.

Business Validation:
Noah Kagan - see his blog

Entrepreneurship:
Tycoon - Peter Jones (Dragon's Den UK!)

Independent authoring:
How I sold 1 million Ebooks in 5 Months! - John Locke