There are a few web authoring tools around, Quanta & Bluefish are the most developed. There is also f4l - Flash 4 Linux that looks like Flash 4 (very Windows 95 look).
If these aren't suitable there is always the option of using CrossOver Office and then installing Macromedia Studio. I'm seriously thinking about this route, the cost of CrossOver Office is getting quite reasonable. You can also lobby Adobe/Macromedia for a Linux version
and see how much they listen.