Normally, I spend less time talking about running a business than about the tax topics that effect businesses.
But even tax nerds like me can change. With that in mind. Recently I picked up a book called "Duct Tape Marketing" by John Jantsch. It is a great book with the premise that every business owner should be a good sales person, whom offers the same attributes as duct tape. Those attributes are versatility, dependability and a good all around resource for "clients". It also talks about many other subjects including creating sticky relationships with your best clients.
I would recommend this book to all small business owners who are looking to make more money, because I guess in the end, that is what marketing is all about.
Beyond marketing, this book does a good job of helping business owners analyze their business in order to improve all the facets of the business and begin to create a cohesive business strategy.
I picked it up on amazon for around $10, so it is also pretty cheap, which I also really enjoyed.