Could someone recommend me of a good Tween library for AS3 (for use with Flash, not Flex)
Tween Lite is supposed to be good; My good-at-flash-friends recommanded it to me. What I found useful that it provided a little flash-app for trying out the different tweens and generating the code snippet for the choosen tween in the same time.
Here's a short list of tween libraries I'm quite familiar with:
And, here's a link to a nice comparison of a suite of different libraries for both AS2 and AS3: http://www.greensock.com/tweening-speed-test/
Ultimately, it's going to come down to which syntax you prefer and which one you're most comfortable with. I suggest you look a few of them over, pick one or two and code up an easy comparison to see for yourself...
Good luck!
I've always found greensock so easy to fall into - it gives you a great script generator with a list of all it can do.
I wrote one called KitchenSync. It's excellent if I may say so.