There are lots of really good tutorials built right into your Flash MX - my first suggestion is to do ALL of them step by step the way it shows you to do them. This will teach you a lot about your software.

Check http://www.macromedia.com - I think that have some online tutorials and classes as well.

You could also go to the message boards at http://www.flashkit.com and pose the same question there. Those folks really know Flash and could probably recommend reading.

I'm fairly proficient in Flash, but not in advanced action scripting, but I'm one of those "manual readers". I pick up the manual, read it through and then play with everything in a program until I feel comfortable with it. This works for some people, but not for others.