I've just finished reading through the wonderful new Android Design site Google just released. A lot of the information is stuff you should already know if you're an Android developer. However, I took notes of pages/information that I found particularly interesting (or new for ICS). Listed in order of appearance on the site:
48dp Rhythm - Like me, you may have implicitly noticed this pattern before, but it's good to see it stated so explicitly. (Same with the 8dp gap.)
Back vs. Up - Having been confused on the exact distinction for a while, this page is a breath of fresh air.
Action Bar Pattern - This entire page should be required reading for everyone. It definitely looks like the Action Bar is the future, and this is the instruction manual.
Long Touch Multiselect - Breaking news: long touch no longer activates the contextual menu. Now, it is purely for activating selection (aka multiselect). Every longtime Android developer should be aware of this change.
(Personally, I didn't even notice this change despite owning a Galaxy Nexus for a month. Perhaps that's because not even every Google app has switched to the new design yet. Or perhaps it's because long touch is just not an intuitive way to design any functionality - I've long since given up putting any core functionality into long touch. Still, it's worth noting the design shift.)
Android is not the iPhone - At least, that's what this section should be called. This page will be most useful for showing to your designer or boss how Android differs from iPhone and why you shouldn't just port assets and design directly from one to the other.