Cool Web 2.0 for k-4

Looking for and sharing k-4 web 2.o tools.

Number one: Kerpoof.com
Powered by Disney; students can create stories, cards, doodles, and animated movie shorts by dragging and dropping. Also comes with great video tutorials. [Free]

Number two: ToonDoo.com
Powered by JamBav; they are working through a beta version that allows teachers to create a classroom specific url. Much like Kerpoof, students create cartoons that are commented on by others. Great for teachers too. Imagine introducing a new concept through a cartoon...

Looking for more if you have any others...