I wish Hypercard had managed to survive as a default install on Macs. It's the perfect first development environment for kids IMHO. You can learn the basics by reading the source in any stack (including the home stack) and there's enough depth that you won't get immediately bored with it. Plus your applications (stacks) are graphical right from the start so it doesn't feel like you're back in the 80s and being amazed when it scrolls out "Hello World" indefinitely.