Like I said in several earlier forum posts, I've been putting together a list of websites that allow you to list your books for free. This list only includes book related websites (I didn't include the numerous social network sites that allow you to do this - perhaps another project). This is another way to get some free exposure for your book and a couple of backlinks for your website.
If you go to the Marketing Your Writing Online
page and look at the first link on the bottom entitled "Free Book Listing Sites" you will find several sites where you can list your book, cover, a blurb, etc.
If you know of some I missed, please let me know and I will add them.