IMO, ActionScript 3.0 seems like another language altogether, as the similarities with ActionScript 1/2 are not that much at all. Developers may have a tough time to learn (I had my own mental block a while ago), and to designers, it seems nearly impossible to start grasping this new powerful, yet daunting to learn language. 
The community has been great though. With reference to Guy Watson aka FlashGuru’s post on ActionScript 3 Resources, Trevor McCauley aka Senocular has written a couple of very useful materials to start learning AS3. They’re definitely a great help over the last few days of AS3 development as I’ve referred to them CONSTANTLY. 😀
- ActionScript 3 Tip of the Day – Over 100 tips and tricks to learn!
- Getting Started with ActionScript 3.0 in Adobe Flash CS3
I definitely recommend getting Colin Moock‘s book on Essential ActionScript 3.0!
Edit: Check out this google search!
