I found these pretty nifty:

replacing TextField and improving performance
http://lab.polygonal.de/2009/04/26/goodbye-textfield/

Round up of ActionScript 3.0 and Flex optimization techniques and practices
http://www.insideria.com/2009/04/51-actionscript-30-and-flex-op.html

Tips on how to write efficient AS3
part 1
part 2

a faster way of tweening (faster than tween max)
Tweensy