2D animation software.....?

Um, does anyone know GOOD AND FREE 2-D animation software FOR MAC. I have Pixen, but it isn’t that great at animation, only pixel art… I tried googling this question several times but I haven’t found anything that I need…

P.S. This isn’t really useful to use WITH blender, but I wasn’t sure where else to post this…

Ummmm… anyone got an answer for me… please?



Update 2008-01-21: v0.4.4b is now available for Mac OS X.
(also available for windows/linux)


Synfig Studio is available for Windows, Linux and MacOS X.

non-free but cheap:
Also available for OSX.

Anime Studio is great, and while not free, its powerful, easy to use and very affordable. Snith Micro run frequent sales and you can hunt around the web for coupon codes. Its sometimes possible to pick up the debut version for around $30.