Google I/O 2011 contained a lot of really valuable information the problem is digging it out of the huge number of videos that have been made available. To help with this problem here are the videos of the Android sessions roughly categorized.
If you are looking for information on the ADK and the Android Arduino connection it is in the Advanced topics group. There is also an interesting overview of Honeycomb in the General/Future group.
Google has released Material Design Lite, a library of components and templates that enable developers to use its material design styling, introduced with Andriod Lollipop, on websites as well as in a [ ... ]