ScaleNine (cool site name by the way) is offering free, high-quality Themes for your Flex 2 apps. There are currently 6 themes in the collection with more coming in the near future. Update: after quite a while I went back to take a look at how actively new skins and themes for Flex 2 are being added and happily I can report that dozens and dozens of absolutely gorgeous and interesting themes are now available on the site.
There is even a provision for Â learning how to create your own skins for Flex and AIR right on the sidebar that I think a lot of developers will have an interest in. But again, it will be a long time before you exhaust the possibilities for teriffic themes already available to you on the site.