Sams Teach Yourself Macromedia Flash 8 in 24 Hours

Although Flash is practically universal, it doesn't hurt to know exactly how popular it really is. This page on the Macromedia site gives a running census of how many people have the Flash and Shockwave players installed:

www.macromedia.com/software/player_census

This is especially useful if you need to report to a third party, such as a client, how compatible a Flash piece is with the general public.