An old friend asked me for advice yesterday about graphics/design programs for her 11-year old son. I was pretty stumped! So I posted the question on an animation mailing list I maintain and got a few responses. I'll use this post to collect them for future reference.
Thus far I'm a bit surprised not to have more kid-specific stuff here, but I'll list it all anyway (highlighting where appropriate the super kid-targeted software).
I'm also going to name a few things that I learned about when we recently got our XO Laptop.
Squeak (kid-oriented, free): a media authoring tool that lets you do paint objects, then build simple scripts for them so they move around procedurally.
Cosmic Blobs (kid-oriented, commercial): neat-looking kids modeling package.
Not specifically kid-oriented, but these are free:
Blender: free high-end 3d software
Wings 3D: free high-end polygonal modeling tool
Seashore: free 2D painting/design software
Not specifically kid-oriented, and not free:
Bryce: commercial 3D software
Photoshop: commercial 2D painting software