I have written, published, and marketed almost a dozen books, so I know what you are going through. You didn't mention whether your books are fiction or non-fiction, or what the genre of your books is; however, I will try to answer your question for all types.
The social media is the obvious area to promote. This includes Twitter (http://Twitter.com ), Facebook (http://Facebook.com ), and LinkedIn (http://LinkedIn.com ). If you haven’t been taking advantage of these platforms, you should start now.
For any new books, you should trying crowdfunding. Use social media to drive people to your Kickstarter or Indiegogo page. Depending on how much people contribute, they could receive the ebook version, the hard copy books, or the book release party.
Go to Meetup.com and attend meetups related to your books, especially if they are non-fiction.
If you don't have a blog yet, start one, related to your books. Post excerpts from your books on you blog with links to your book page on Amazon. Also, at the back of all your books, post the URL to your blog.
For the non-fiction books, call museums across the country that relate to your book topic and ask to speak to the manager of the museum gift shop. Then ask if they would be willing to buy your book to resell at the museum.
Finally, give speeches anywhere you can to any groups that may be interested in having you speak. Your speech doesn't even need to relate to your book topics. You could talk about writing in general: how you got into writing, how you were able to stay dedicated to writing, how you got published, and tips for anyone who ants to write and publish a book. Then sell your books at the end of your speech. Make sure to tell each buyer of your book that you would appreciate it if they leave feedback for you on Amazon if they are so inclined.
I go into a lot of details on book marketing in my latest book, Write a Book in 30 Days Publish in 30 minutes ( http://www.amazon.com/Write-Book-Days-Publish-Minutes/dp/1515234819/ ). Also, please schedule a call for more information and follow-up questions.