wp2epub generate epub files, ready to publish, for iPad, iPhone and other readers. Just choose the tags, categories or dates to export. It’s done. You are now a bloguer and a writer. wp2epub also export in html, and then you can open with a wordprocessor to convert into PDF or other formats. A good way to backup your blog. Possible integration on each post.
This plugin is available for download to be used on your WordPress self-hosted installation.