From Google Webmaster Central, a post with the Best uses of Flash. The 3 main suggestions are:

1. Try to use Flash only where it is needed. Many rich media sites such as Google’s YouTube use Flash for rich media but rely on HTML for content and navigation. You can too, by limiting Flash to on-page accents and rich media, not content and navigation. In addition to making your site Googlebot-friendly, this makes you site accessible to a larger audience, including, for example, blind people using screen readers, users of old or non-standard browsers, and those on limited low-bandwidth connections such as on a cell phone or PDA. As a bonus, your visitors can use bookmarks effectively, and can email links to your pages to their friends.
2. sIFR: Some websites use Flash to force the browser to display headers, pull quotes, or other textual elements in a font that the user may not have installed on their computer. A technique like sIFR still lets non-Flash readers read a page, since the content/navigation is actually in the HTML — it’s just displayed by an embedded Flash object.
3. Non-Flash Versions: A common way that we see Flash used is as a front page “splash screen” where the root URL of a website has a Flash intro that links to HTML content deeper into the site. In this case, make sure there is a regular HTML link on that front page to a non-Flash page where a user can navigate throughout your site without the need for Flash.

However, as John Dowdell says, “The author misses completely, however, the subject of how people will actually search for you — to figure out on which plausible search terms you can compete, and optimize your text to place highly on those specific terms, rather than worrying about Google databasing every single word in the project.”

Brgds,

CP