The community’s cry for a simple guide that would quickly go over some of the most felt changes from AS2 to AS3 has been heard. Adobe has recently added a new resource to the ActionScript Center called the ActionScript 3 Migration Cookbook.
There you will find a quick introduction to migrating to ActionScript 3.0 from ActionScript 2.0. It is targeted at designers and developers who have some experience scripting content within Adobe Flash CS4 Professional. It does not require an understanding of object-oriented programming.
Along with this resource of common AS2 code into AS3 conversions is a a downloadable PDF version which basically takes this section of the Devent site and dumps it into a portable version. Overall, this is a nice guide that can provide that helping hand during the first stages of the migration over to AS3.
Download the ActionScript 3 migration cookbook