Replica Island is a free open source android game. If you ever wanted to see how a game is build here is your chance - though be careful since the project is not that new anymore, things may be done differently in newer versions of Android.
ActionBarSherlock (github.com)
Android library for implementing the action bar design pattern using the native ActionBar on 3.0+ and a custom implementation on pre-3.0 through a single API and theme.
Bash completion for the adb tool (code.google.com)
Roman Nurik has hacked together a great bash completion for the adb tool.
Android Development Tool 17 (Preview) was released yesterday. Lot's of neat stuff inside.
Ever wanted to make a screenshot of your newly developed Android App? With Android Screen Monitor you can mirror the device screen to your desktop.
m2e Android Configurator (github.com)
m2e Android Configurator brings Maven dependency management into the ADT.
This video demonstrates how to use AndoidStudio add-in in Visual studio for Android application development.
Schooltraq (beta.schooltraq.com)
Schooltraq is a free academic planner that lets students organise their work.