The Flex 3 public beta marks a big step toward the availability of Flex under an open source community process. Adobe is now making a detailed feature roadmap available for Flex. Additionally, Flex developers now have public access to updated nightly builds and to the production Flex bug system. External users can now log and track issues and feature requests in this system. You can find all of the open source Flex information today at Adobe Labs - Adobe Flex.

System Configuration for Flex builder
Windows
Intel® Pentium® 4 processor
1GB of RAM recommended
Microsoft® Windows® XP (with Service Pack 2)
Microsoft® Vista Home Premium or higher
300MB of available hard-disk space to install
Java™ Virtual Machine: Sun JRE 1.4.2 (included), Sun JRE 1.5, IBM JRE 1.5
Eclipse 3.2.1 or higher for Plug-in install
New Flex Builder 3 projects create applications that require users to have Flash Player 9.0.28 or higher. You can change this to an earlier version of Player 9 in the Flex Compiler section of your project's Properties.

Macintosh
G4 1.25 GHz PowerPC or Intel based Mac
OS X 10.4.7 - 10.4.9
1GB of RAM recommended
300MB of available hard-disk space to install
Java™ Virtual Machine: JRE 1.5 or JRE 1.6 from Apple
Eclipse 3.2.1 or higher for Plug-in install
New Flex Builder 3 projects create applications that require users to have Flash Player 9.0.28 or higher. You can change this to an earlier version of Player 9 in the Flex Compiler section of your project's Properties.

thanks

__________________
Karpagarajan. R
Necessity is the mother of invention