Until now, creating a site in Flash was a sure fire way to guarantee zero search engine visibility. Sure, there were things you could do like sIFR and SWFObject, but these and other work-arounds required some extra work and a level of expertise. Adobe just announced that they are working with Google and Yahoo to make Flash indexable to the search engines. This is a huge step that will certainly make a lot of graphic designers very happy. Don't let this news lull you into a false sense of security. This doesn't mean that Flash sites will all of a sudden shoot to the top of the rankings. In fact, all that will be indexed is the text elements of the Flash file, so you should pay close attention to the text you use. Many Flash sites use text sparingly (which is often why they used Flash in the first place), so you've still got a lot of SEO work ahead of you to see any kind of real results in terms of top rankings. You've still got to pick the right keywords and write strong content. Also, don't start thinking Flash is the answer to all your problems. You should still use Flash sparingly, and only when it makes sense. You've still got issues with deep linking (they're working on it), and other issues that are more easily solved with HTML pages, but at least Flash doesn't suck as badly for SEO as it used to.
Google has already rolled this out and Yahoo is working on it and "expects to deliver improved Web search capabilities for SWF applications in a future update to Yahoo! Search."