I spent the better part of four years before the keyboard as a graphic designer, but when it comes to programming and development, I don't know Java from a small Indonesian island. If you're a designer who's been tasked with creating the visual elements for an Android app, you need to check out Peter Nohejl's Android cheatsheet for Graphic designers. It's got pretty much everything you'll need when preparing visual assets, plus bonus help when preparing promotional materials for the Play Store.
In addition to basic dimensions, DPI settings, standard colors and the like, there's some great information about why you need to prepare certain files and templates in certain ways. Take the handy table of screen densities and icon sizes: in a quick glance, you can determine the sizes you'll need for various icons, on screens of different sizes and densities. (Plus it's got the ever-confusing shorthand for mobile resolutions, like xhdpi.)
Links in every section go out to even more resources, like standard guidelines and assets, naming conventions, and the various tools that have already been created. There are also quick downloads for templates and Photoshop shapes. This thing deserves a permanent spot in any mobile designer or UX professional's bookmark folder. Follow these guidelines, and the folks in /r/Android will love you forever.
Android cheatsheet for Graphic designers - Peter Nohejl
P.S. App developers, if you want a little more exposure in Android Police's bi-weekly app and game roundups, post at least six screenshots and a video to the Play Store.