Here a video from Google I/O 2009 with Romain Guy from Google.
"Learn practical tips, techniques and tricks for making your Android applications fast and responsive. This session focussed on optimizations recommended by the Android framework team to make the best use of the UI toolkit."
.. Very interesting stuff. I would really encourage everyone to watch this.
Covers: Adapters, View & Layouts, Backgrounds & images, memory allocation and Drawing & invalidating.