I have been working with Flash for 7 years.
It can be used to make games, animation, videos, adverts, music players and even websites such as this. These are used on almost every corporate website because they make an impact and allow the site to maintain their brand image. And because Flash is vector-based, these can be output at broadcast quality for tv or output for print. (Most animated ads on TV are now done in Flash - see Sky TV)
With clever use of actionscript , you can let the user print from the online movie (vouchers, advertising materials, order forms, etc), order straight from the page through a secure server, have their own password for protected areas, keep notes on their own page; the possibilities are endless, and only limited by your imagination as you can see from the examples below.

A range of uses for Flash, from simple banner ads to self-contained interactive applications