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 Mastering Ansible, so I picked up some different ways to think about working with Ansible.
I skipped on to Ansible for DevOps: Server and configuration management for humans written by Jeff Geerling, a pretty active Ansible community member. I like this book the best so far. I haven't finished this or Ansible: Up and Running yet.
I bought Ansible Playbook Essentials but I haven't started it. I was hoping it would have a bunch of interesting examples and problem solving techniques. However, looking through the Table of Contents, I think it will cover pretty much the same stuff as the other books.
A guy named Brian Coca has a series of amusing gonzo Ansible hackery. I created a plalylist titled Ansible Tips & Tricks
Jeff Geerling, the author above, maded a fun video Ansible 101 - on a Cluster of Raspberry Pi 2s