I had been searching for a good lightweight text editor to develop Actionscript 3 on Linux, but there wasn't much out there. Eventually, I decided to make a custom options file for the SciTE text editor to support Actionscript 3 and the Flex SDK. This is the result, if anyone out there is looking for something similar.
This project is no longer maintained.
SciTE AS3 1.1
See the included readme.txt for install instructions.
SciTE AS3 1.0