Android Architecture

An overview of Android components, and a diagram of the architecture are available at http://developer.android.com/guide/basics/what-is-android.html

The diagram on that page appears in every presentation I have ever seen regarding Android technical topics (with the exception of my own).

A quick look at Android contents and programs running when Android starts is at:
 * http://benno.id.au/blog/2007/11/13/android-under-the-hood