Although it's not designed for this purpose - I found the drawing tools in Flash to be far superior and more intuitive than vectored programs such as Illustrator and Freehand.
With vectored programs you have to learn all about Bezier curves and deal with those handle thingies, layers, fills, and all the whistles that make it go "wow" - with Flash you just install a drawing tablet and go at it.
Pencil, eraser, fills, all this is a natural extension of traditional paper and ink, it's way more intuitive to use as a drawing tool.
The artwork can be exported in any .bmp format. An added bonus, it can also be exported as EPS and managed in any vector program. Then there's the whole animation deal . . . :-)