Drew Mclellen nearly had kittens when he discovered a method of embedding Flash movies into web pages while maintaining the mark-up's validity. He explains all in this weeks A List Apart.
It's probably worth pointing out that validity doesn't necessarily mean accessibility; there's nothing to stop someone designing a monstrous flash based site only to stick it between some validating HTML tags and claiming web design excellence.
I'm sure that this discovery will please many web designers using Flash who are also conscious of web standards. But I think it's going to take much more work on the part of Macromedia, W3C and the browser manufacturers before we have a proper solution to the Flash accessibility problem.