Some flash sites put alternate content to be visible by search engines.
There are many different ways to do this. Some sites has searchable text at the bottom of the page, some others have the full representation of the flash content in HTML displayed only if flash doesn't work.
When I'm developing a Flash based site, I embed the Flash swf file in a HTML page.
This way I can add META data to the HTML page for Google to index.
When you create a Flash animation, check to be sure that Flash is also generating a HTML file. Once the file has been created, you can then add META data to it. Upload it and Google can take care of the rest.