As an #Android Developer Advocate I spend a lot of time working with partners. They are, fortunately, all aware of our main resource at developer.android.com however I often refer them to our resources at the Android Design site (http://developer.android.com/design), the Android Developers Blog (http://android-developers.blogspot.com) and +Android Developers they are all excellent. But the 3 specific links I find myself sending out most frequently are:

Android Developers Blog | Making Android Games That Play Nice - http://android-developers.blogspot.com/2011/11/making-android-games-that-play-nice.html

Android Design | Pure Android - http://developer.android.com/design/patterns/pure-android.html

Android Developers Blog | Android Market Feature-Image Guidelines - http://android-developers.blogspot.com/2011/10/android-market-featured-image.html

More recently Android Training (http://developer.android.com/training) has also joined the list of indispensable sites and the public guidance on Loading Large Bitmaps Efficiently is really helping many developers (http://developer.android.com/training/displaying-bitmaps/index.html) as well as the other classes and the basic training I linked to yesterday.
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