So today at Adobe MAX a huge announcement came out. We now have special tooling that allows you to use the Flash Platform to build applications for the iPhone. Flash developers will be empowered to use their existing skills to construct applications for iPhone that can be distributed through Apple’s App Store. No promises but the betas of this (CS5) should be available by the end of this year.
Exciting stuff. It sounds like plan won't necessarily allow for Mobile Safari to have a plug in, but that developers will be able to develop with Flash/Flex and then go through the App Store routine to get distribution. So this might not be the golden ring everyone wanted (to use their favorite flash-enabled sites), it is quite interesting for experienced Flash developers.
See some examples and a few FAQs over at Adobe.