SWFTools is an open-source SWF (Flash) library and toolkit I started together with Rainer Böhme and have now been actively maintaining for over ten years.
It contains a multitude of utilities and converters, which can generate Flash files from audio files, video files or text documents (PDF). It also contains disassembler and assembler for ActionScript 3, as well as a scripting language (swfc) for generating complex animations with just a few lines of code.