Are there any free tools to create SWF / Flash animations?

Are there any competitor tools like Flash for creating SWF animations? My 8 year old son wants to learn 2D animation but I doubt his anticipated attention span warrants buying Flash.

From stackoverflow

• The following URL contains a rather comprehensive list of open source flash projects. Take a look, you might find what you need.

  http://osflash.org/open_source_flash_projects

• There's a short video tutorial on using InkScape and SWFTools to make an animation here:

  http://screencasters.heathenx.org/episode-031/

  Alternately, you could look into the (now discontinued) PowerBullet which has a PowerPoint-like interface.

• It's not "free" as such, but there's a 30 day trial for Flash CS4 up on adobes site.

• For kids there's a software called ANIMATIONISH. It's not free, however. This was made by the guys who created ToonBoom studio (a pro software for 2d animation).