A series of tutorials from Googler Chet Hasae and others, answering most commonly asked question: “What are some of the important rules to keep in mind when developing Android applications?
Official site provides the SDK, Developer’s Guide, Reference, and Android Market for the open source project. Includes announcements, videos, and blogs.
Learn how to create an Android app by following along with the pros in these video tutorials. Build Android apps from scratch or incorporate Java applications into your Android development process.
Tutorials about development for Android: tools installation, debugging, using Fragments and the ActionBar, file and network access and other topics.
Very good tutorials by Lars Vogel.