The Author Showcase plugin allows authors to display their books, with buy links, on their website in a nicely formatted style.

The dotEPUB plugin automatically adds a "Download as an e-book" button or link to your blog posts.

A WordPress Bookstore Plugin to help authors boost book sales on sites like Amazon and Apple iBooks with great-looking book pages.

A simple widget for adding links to your books for sale on sites like Amazon, Kobo, Nook, etc.