My development environment varies based on the project that I'm working with. For my latest project I'm creating a Flex media player and though I started using Gedit, I've moved to Eclipse + Flex Builder so as to take advantage of Flex's Builders code completion feature. Other features that I needed for this project were support for FTP, Bazaar, PHP, and JQuery. Here are the steps I took to build the IDE for this project.
If you haven't heard, Adobe recently published the Flex in a Week video series. The bummer for us Linux users is that to watch the videos you need to install AMP, which is not compatible. However, today I found that you can watch the videos if you import the video series xml feed into Miro.