I'm no Android developer, but I figure if I wanted to get started, I'd check out some videos and pick up a couple of books. That leads to the obvious question: where are these things? Packt, a publisher of both eBooks and good old-fashioned print ones, is currently offering its full catalog of development-oriented works for $5 each (in digital format only). It's also offering a few videos at the same price.
Some of the books are very specific, providing guidance on how to develop voice applications or dabble around with augmented reality (there's even one for working with OUYA). Others are general. The thing is, Android changes a lot from one release to the next, and some of these works deal with older versions that aren't nearly as relevant today. A book from 2012 may not sound old, but think about how much has changed in the world of Android since then.
As mentioned before, content doesn't just come in the form of books. There's a video on developing using Unity 3D and another on creating apps using PhoneGap. There aren't many, but you can find a couple if you browse for a bit.
Anyone looking to supplement their journey into Android development and programming in general should take a quick glance at the link below.