Hi,

I would suggest you first go through Android Developer Guide http://developer.android.com/guide/index.html
It will give you good start.
Then you can start learning from Blogs.
Here are some of blogs which helped me a lot in Learning Android.

http://saigeethamn.blogspot.com/2010/05/table-of-contents.html
http://www.vogella.de/articles/Android/article.html
http://mobile.tutsplus.com/tag/android/
http://mylifewithandroid.blogspot.com/
http://tutorials.jenkov.com/
http://developer.android.com/guide/index.html
http://marakana.com/forums/android/examples/
http://mobiforge.com/Developing

Have Fun In Android..
Vipul

Beginning Android Application Development Ebook

http://androidcontrol.blogspot.com/2011/10/beginning-android-application.html

How do we learn this? I want to learn