I am a big Scratch lover, though my current job has little ability to spread the word. If you look around Engage, you will find lots of resources here entered by others...use the search bar!
Be sure to join the ScratchEd network as well!
Here's a wiki with tons of Scratch resources...
And of course, the original group- the Lifelong Kindergarten Group at MIT!
Luke, I've been a big fan of Scratch since it was called Squeak (that was awhile back). I appeciate that it's an online tool, sort of an App before there were Apps. Also appreciate the collaborative environment in Scratch, kids can share their projects and discuss their work. Mitch Resnick has done some pretty amazing things with the Lifelong Kindergarten Program at MIT. He's the modern day Friedrich Fröbel. Remember him from Education 101? Frobel coined the word Kindergarten and was one of the first to promote learning though play. A real good "read" is Inventing Kindergarten, by Norman Brosterman (a biography of sorts about Frobel).