Google Android is becoming more and more popular with the growth of the G1 and with the upcomming new phone release.
I was checking on some documentation to see how to develop applications to the Android and I found this site (kind of slow) that have some great documentation for beginners: http://www.brighthub.com/
Here is the list of the documentation for developing Android applications:
1. Setting the Environment: Using Eclipse and Netbeans For Developing Google Android Apps
2. How-to create an Android Application: Structure I
3. How do I Develop an Android Application? Structure II
4. How-to create User Interfaces (UI) using XML : Layouts
5. How-to create an User Interface (UI) using XML : Widgets
Check it all. It will be worth your time and reading.