I think everyone now will be hearing a noise about Flex. Well, this is a new way to create an swf in very sort. So before what, why and how, if you just want to see some of your Flexcode to be in action then, this is the answer. This is an online compiler for your flex applications.Without even installing a single component in your pc, you can just copy paste your code into the code area of this very site and see your swf will be created online.
Give it a try, you will love it.