Join Goodreads.com and become a Goodreads author. Join some groups that focus on the type of book you wrote. Introduce yourself in the intro topic, then see if they allow authors to create a promo thread. Be active -- don't just promote and leave. Talk about the books you love with like-minded people. Those who share your taste in books might like the book you've written.
If you have a print copy of your book, consider hosting a giveaway at Goodreads. That's a great way to get a bunch of people to take a look at your blurb! Some may add it to their to-read list, even if they don't win the giveaway.
Join LibraryThing and become a LT Author. Consider hosting a giveaway in exchange for reviews. They'll let you giveaway ebooks, too.
Seek out bloggers who blog about the kind of book you've written, and ask for a review. You'll need to be able to send them a free copy of your book. Some don't review self-published authors, and some don't review ebooks, so you'll need to research them a little.
Encourage those who've read your book to write a review. Doesn't have to be a long essay -- just a couple sentences on why they liked it and/or recommend it. Word of mouth is the best marketing tool ever, and reviews are one form of that. Don't badger them -- people who've written ONE review, on YOUR book, may be assumed by other readers to be your relative, and their review may be suspect.
If you come across bloggers who interview authors, volunteer! Being interviewed is a great way to draw attention to you and your writing.
Participate in forums that discuss books, like http://www.bookandreader.com/forums/ -- don't promo there (you might get banned), but do put a link to your book in your signature. When you show up regularly, people will get curious and click. Don't be afraid of posting in the Amazon community -- just don't spam those forums with pleas to buy your book (unless you post in threads specifically created for that purpose).
Create a fan page for the book at Facebook. (If you don't already have a facebook account, create one for your author persona.) Invite all your friends to "Like" the page.