One of the tools we use extensively is MIT's scratch software.
Scratch helps young people learn essential skills for life in the 21st century: to think creatively, reason systematically, and work collaboratively.
Scratch is a project of the Lifelong Kindergarten Group at the MIT Media Lab. It is provided free of charge and children will be able to build on their knowledge acquired during lessons at home.
Here are a few articles and research papers that explains the effectiveness of scratch.
Learning with scratch
An introduction to the research
A full list of sources
Let us know if you're active on scratch we would love to see your work!
For some of the students work have a look here: