source.android.com
Examples in SDK
- http://code.google.com/p/shelves/
- http://code.google.com/p/apps-for-android/
- http://code.google.com/p/foursquared/
- http://code.google.com/p/zxing/
I'd also recommend search public repos such as code.google.com, github, bitbucket for keyword android.