Thinking, fast and slow, Daniel Kahneman - This is the best book I have ever read that relates to practical application of skills. Although its not specifically related to business or internet marketing, its about the psychology of the mind and what influences the way we think about things. I think about this book all of the time in my day to day business life and its been a big influence for me.
Straight line persuation, jordan belfort - Not a book, but a course that you can probably find online somewhere. This is another very influential piece of material that I think about, and use, all the time in my day to day business life. As well as personal life. This really made me think about how to influence people and although its about sales, it can be applied to absolutely everything because it teaches you how to communicate, how to get people to do what you want and also it helps when dealing with other people that are trying to sell things to you - whether it be products or ideas or anything else.
How to win friends and influence people, Dale Carnegie - Another amazing book. This also comes to mind often and its a great book for learning about what makes people tick and how you can work people around to your way of thinking. Once again this could be related to selling someone something, or just getting people to do what you want.