Eric Anderson has written a good overview of some of the new features in the Flex 2 beta 2 release that is on labs right now. This includes
- Flex Framework 2
- new and free Flex 2 SDK (which includes the compiler and framework)
- ActionScript 3
- Flex Builder 2.0
- Flash Player 8.5
You can read the entire article here.
You can download all of the bits from labs.