Check out this article by Paul Sloane. I really like his thinking.
http://www.lifehack.org/articles/communication/ten-great-ways-to-promote-your-book.html
Here are five sample ideas. For all ten, go to the source.
5. Offer sample chapters as free downloads. Take a couple of your best chapters and turn them into pdf files. Let people download them for free. Think of this as the equivalent of letting people browse through your book at a bookstore.
6. Use material from the book in your blog. Start a blog and quote from the book. Lift sections and acknowledge the book as the source. Build a community of interest around the topics in the book.
7. Review other books in this field. Become a reviewer on Amazon. Use your own name accompanied by ‘author of the book……’. Review other books and when people read your reviews some will click through to your book.
9. Give away copies to the right people. Use the book as your calling card. Give copies to potential and existing clients. Encourage them to read it and pass it on.
10. Offer books as prizes. Local radio shows, magazines or societies will often be interested in running competitions and will give you valuable publicity if you give them a few books to give away as prizes.