See Google's What is Android? page for an overview of Android components, and a diagram of the architecture.
The diagram on that page appears in every presentation I have ever seen about Android technical topics (with the exception of my own).
Here is the Android Architecture Diagram]
Breakdown of running Android system
A quick look at Android contents and programs running when Android starts is at:
Relation to the Linux kernel
Here is Greg Kroah-Hartmans presentation on Android from the CELF conference 2010, discussing how Google/Android work (or don't work) with the Linux community.