There is a video course on Pluralsight called Hands-on Ansible. It's pretty good, and includes a bit of content on Vagrant, since that's a nice way to spin up several disposable servers locally.
Ansible (the company) has a few introductory videos on their Ansible Resources page. Requires submitting an email address and a browser that allows Flash.
I started with Mastering Ansible from Pack Publishing first, since it was at the top of the search results in Safari Books Online. It pretty good, but didn't seem remarkably different than the Ansible Documentation
I bough a bunch of eBooks from Amazon. I started with Ansible: Up and Running from O'Reilly. It's a solid book, and differed from Maste