Flex 4 is certain to mold the future of RIA development. Building on the existing Halo theme the Flex Team has started to further refine the component model and architecture for Flex. Flex 4 has a strong focus on design. One primary goal is to allow designers and developers to collaborate in innovative and unseen ways bending the RIA paradigm and pushing the expressive envelope even further.

Here is a useful list of links for finding information about Flex 4 - Gumbo. From getting started to the new skinning features this list of links will help introduce you to Flex 4.

“Gumbo plan” video - Matt Chotin
http://flexorg.wip3.adobe.com/gumbo/gumboplan.htm

Flex Bug Database - Filtered to show 4 Gumbo Bugs

http://snurl.com/39jlk

Gumbo Themes
http://opensource.adobe.com/wiki/display/flexsdk/Gumbo+Themes

An Introduction to the Gumbo Component Architecture
http://opensource.adobe.com/wiki/display/flexsdk/Gumbo+Component+Architecture

Compiling Your First Flex 4 Application
http://blog.smartlogicsolutions.com/2008/07/15/compiling-your-first-flex-4-application/

Compiling Flex 4 (Gumbo)
http://sherifabdou.com/2008/07/compiling-flex-4-gumbo/

Adobe® Flex™ Gumbo Language Reference
http://livedocs.adobe.com/flex/gumbo/langref/

Gumbo Downloads from Adobe
http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4

Flex 4.0 Gumbo ~ Developer Designer workflow, just awesome
http://bkflex.wordpress.com/2008/07/15/flex-40-gumbo-developer-designer-workflow-just-awesome/

Using the beta Gumbo SDK in Flex Builder 3
http://blog.flexexamples.com/2008/08/02/using-the-beta-gumbo-sdk-in-flex-builder-3/

Downloading and installing Flex SDK builds from opensource.adobe.com
http://blog.flexexamples.com/2008/08/01/downloading-and-installing-flex-sdk-builds-from-opensourceadobecom/

Jumping Into Skinning with Flex 4
http://scalenine.com/blog/2008/07/17/jumping-into-skinning-with-flex-4/

Gumbo (Flex 4) Skin with Transitions
http://scalenine.com/blog/2008/07/20/gumbo-flex-4-skin-with-transitions/

Flex 4 (Gumbo) VSlider, HSlider, Panel Skinny Example
http://sherifabdou.com/2008/07/flex-4-gumbo-vslider-hslider-panel-skinny-example/

Flex 4(Gumbo) using the includeIn Property and States
http://sherifabdou.com/2008/07/flex-4gumbo-using-the-includein-property-and-states/

FXG kicks ass!
http://www.richapps.de/?p=156

ILOG Elixir Gauges using Flex 4 (aka Gumbo) FXG
http://blogs.ilog.com/elixir/2008/07/18/ilog-elixir-gauges-using-flex-4-aka-gumbo-fxg/

If you are Trying to Compile Gumbo (Flex 4) and getting a Verify Error
http://sherifabdou.com/2008/07/if-you-are-trying-to-compile-gumbo-flex-4-and-getting-a-verify-error/

Flex-mojos compiling Flex 4 Gumbo?
http://blog.flex-mojos.info/2008/07/16/flex-mojos-compiling-flex-4-gumbo/

A couple other related, useful links:

Cygwin
http://www.cygwin.com/

J2SE 5.0_13
http://java.sun.com/products/archive/j2se/5.0_13/index.html

Ant 1.7.0
http://archive.apache.org/dist/ant/binaries/apache-ant-1.7.0-bin.zip

mm.cfg
http://opensource.adobe.com/wiki/download/attachments/2392481/mm.cfg?version=1

FlexSDK.cfg
http://opensource.adobe.com/wiki/download/attachments/2392481/FlexSDK.cfg?version=1