It's not so much a question of learning actionscript fast as learning actionscript well. There's also the question of what you want to use it for - flash and actionscript is used for anything from artistic animation to producing business applications.

That said, I think the fastest route is lynda.com and if you want a book for actionscript 3.0 then "Learning ActionScript 3.0: A Beginner's Guide" is highly recommended.

Other possibilities: Foundation Actionscript 3.0 Animation: Making Things Move!

and the fabulous : http://www.cartoonsmart.com/

As I said, it all depands what you want to do with flash.

Paul