Get The Flash xx Bible by Robert Reinhardt & Jon Lentz. At least in Flash 5 it's much better than the lousy tutorials packaged with Flash.
Flash is an interesting tool to pick up, since it's currently a better cross-platform langauge than java in some situations, mostly because a much higher perecentage of users have the plugin installed than an up-to-date JVM. Your app is also a single, self-contained file that can include images and music files that runs without an install step.
The programming model is weird though, it's oriented towards movie frames amd movie clips rather than windows.