Flash

Adobe Flash is an extremely versatile application program that can be used to create animations, interactive web pages, and even functioning programs and computer games. It is primarily a vector*-based application, though it can import bitmap image files.
*Vector graphics are resolution independent files that, unlike bitmaps, are not built with grids of colored pixels, but mathematically generated lines and fills that can be scaled up and down without loss of sharpness and detail. Because of this, the file size of a flash file can be quite small, making it ideal for internet delivery.
Flash concepts
Flash buttons

Resources

Preloaders
BestFlashAnimationSite.com has instructions and dowloads for creating a preloader in your flash movie.

Scrolling Menus
Kirupa.net has a tutorial and download for an 'eternal scrolling menu'Here's another scrolling menu at LayoutGalaxy.com

Media Players
TheGoldenMean.com has an MP3 jukebox you can modify and use for your own website.

Flash tutorials, etc.
VineyarDesigns has a good project-based tutorial on animating a train.
RNEL.net has a collection of online lessons.
Here's some on using Actionscript 3.0