While the server-side components of Flex and Grails used in this book are all available open source, you will find they are not enough to get the work done. In the following section, I will outline some useful tools and libraries that might help in the development and testing of Grails applications. As a java developer that was new to Flex and Grails, it took a little time to discover all these tools, so I thought it might be helpful to include them together for your reference.

IDEs and Text Editors

For Flex
FlashDevelop ( Windows Only ) - Flash Develop is an open source editor released under the MIT License. It offers excellent support for ActionScript and
FDT 3.2 - FDT is a very powerful cross-platform ActionScript and MXML editor and compiler. It is also available as an Eclipse plugin.
Flash Catalyst -
Flash Builder -

For Grails
Eclipse -
Netbeans -
TextMate -
IntelliJ Idea -

Tools and Utilities

For Flex
Monster Debugger -
BlazeMonster - This tool can be used to generate both the server side code to expose Java objects as Remoting destinations and the client side code to connect to web services.
FxSpy - Enables you to change the styling and look of your Flex 2 and 3 projects.
ReflexUtil - Allows changing properties of Flex components while they are running.
FlashTracer - A firefox extension that shows the output of the Flex trace() statement
FlashSwitcher - Let's you switch between versions of Flash in Firefox.

For Grails
Grails Console
Maven
Ant
Gant
Gradle
Hudson

Recommendations

Interface Designers
Front-end Developers
Back-end Developers