ming is truly excellent,
but also recommendable is freemovie,
[shameless plug for somebody else]
The FreeMovie library is a library of PHP, Python, Perl, Ruby, and Tcl functions that generate Flash (SWF) files. FreeMovie can be used to develop Web and desktop aplications.
[/shameless plug for somebody else]
The PHP port is ready for downloading, checkout this site for more info, I'm still waiting for the perl port ;(
som more choices though
If you want a complete drawing program:
very basic but free:
very (very beta) early stage animator LOUNGE
some really cool tools are found here
that's all I can think off right now,
but remember, flashMX is ALWAYS the best you can get though.