Android Usefull Lirbarys

1.Android Twitter Button

2.Android HTTP library
   http://code.google.com/p/android-query/wiki/AsyncAPI

3.Android Image Loader

4.ActionBarSherlock - ActionBar for older Android versions

5.Pull to Referesh

5.Android Annotation framework

6.Dagger - dependency injection framework for java and Android

7. Ploaris - Google maps improvements based on API v1

8.Sliding Menu implementation (1) or   Sliding Menu implementation (2)

8.Downport of animation framework to Android versionas of 1.6 from jake Wharton

9.Otto- Event Bus for Android

10.AChatEngine - Charting Engine

11.ormLight ORM mapper

12.GreeDAO from Markus junginger , ORM Mapper

13.RoboGiuce for testing on the java virtual machine

14. Android Scripting  - Allows to run scripting languages on Android

15.Google Json Parser for Android

16.android-simple-facebook