I just ran into a great post for integrating the Flex SDK with Eclipse. Adobe makes a free software version of the Flex SDK. When you look around for getting started with Flex Builder, just about everything points to Flex Builder, which isn’t available for GNU/Linux anymore. It is built on top of Eclipse, so I don’t know why adobe did this, but it is just one more reason to use free software tools that some vendor can’t jerk you in their direction. Springsource has some great projects working with the Flex SDK.