SWFAddress is a small script that sits on top of SWFObject and provides deep linking for Flash websites and applications. In other words it enables the Back, Forward and Refresh buttons of the browser and creates unique URLs with page titles that can be sent over email or IM.
Their samples work amazingly well, and it is extremely simple to implement -- they even provide AS2 and AS3 classes to use. It supports all major browsers including IE 6/7, FireFox 1.5/2, Safari 2.04+ and Opera 9.02. Finally, this may be the end of one of the largest usability gripes about Flash!