Adobe just released Flex builder 3 SDK and Professional. Professional is an eclipse based developer tool where you can debug and design the user interface. Professional includes support for building desktop applications with Adobe AIR. With Adobe air you can deploy your flex applications to dekstops and on different operating system. The Flex SDK is the open source version and has ant and bat scripts to compile and run the flex applications.
You can download Flex 3 Professional and SDK here
Here are some great links of the possibilities of flex
Flex show case
Flex 3 components explorer
Flex 3 style explorer
Java and Flex
The coming weeks I will build some test applications where I want to build Flex applications on sdo web services and to try to integrate Flex with ADF applications.