Android :
http://developer.android.com/guide/basics/what-is-android.html

Application Fundamentals:http://developer.android.com/guide/topics/fundamentals.html

Hello World program:http://developer.android.com/guide/tutorials/hello-world.html

Hello Views:http://developer.android.com/guide/tutorials/views/index.html

NotePad Tutorial:http://developer.android.com/guide/tutorials/notepad/index.html

Sample Code: 
http://developer.android.com/guide/samples/index.html

Developing In Eclipse:http://developer.android.com/guide/developing/eclipse-adt.html 

Android Tools:http://developer.android.com/guide/developing/tools/index.html