Billboard is an Android app I worked on in 2011 to familiarize myself with the Android SDK. It's primary function is to display large text on the screen, which is actually more useful than it sounds.
Although the app itself is pretty simple I was able to learn a lot about how Android handles views and dialogs, interfaces with a SQLite database, and the basics of drawing to a screen using canvas. The app is open source, and will be available on Google Play as soon as I get the time to hunt down the remaining bugs.