Adobe Flash is one of the VERY FEW programs that will make flash files. Of course, it costs money. There is another program out there that is much cheaper and watered down in features, called Swish.
http://www.swishzone.com/index.php?area=products&product=max
Another Program is even more watered down and even cheaper, called Sothink SWF Quicker.
http://www.sothink.com/product/swfquicker/
There are very few freeware programs concerning flash. I don't know much about them other than that many people complain that there's a horribly steep learning curve to use them and they are overly complicated to try and get to work at all.
So if you're feeling bold you could TRY the free alternatives:
FAMES
http://www.osflash.org/getting_started_with_fames
A bundle of programs that, when working together, can supposedly create flash animations.
FlashDevelop
http://www.flashmagazine.com/reviews/detail/flashdevelop_20/
Latest releases are here:
http://www.flashdevelop.org/community/viewforum.php?f=11
Honestly?
While I support freeware, when it comes to Flash, if I were you I would look up a few basic flash tutorials until you're confident you can use Flash. THEN download Adobe Flash's trial and work with it (Repeat: Tutorials first, THEN flash trial).
I learned the basics of Flash before downloading it, and was able to complete my first two flash animations within the trial period.
See if animating is what you really want to do before you fuss with complicated programs. Animating is a lot more time-consuming and long process than you may think.