Best app I've seen so far in terms of supporting student exploration in 21st century skill development. Basically, kids can explore and experiment with creating their own programs from a visual object basis rather than having to know a lot of code! I tried Jasper's "Grow a Tree" project. It was his second Scratch project using sound. Took me 3 tries to grow my tree... first 2 died. Sorry, Jasper!
Mitchel Resnick offers a great 'effects' tutorial here.
Can't wait to get started using Scratch with my kids! Can you?