There are lots of people who are very comfortable with the Scratch programming environment but want to try something with Arduino to Blink Lights, Sense Buttons, Run Servos or whatever. They may find the C programming environment in Arduino IDE - Sketch, a bit too much of a step.
This instructable draws on the work of the guys at “Citilab” http://seaside.citilab.eu/scratch
They have created a modified version of Scratch to interface with Arduino.
Using Scratch Programs you can make Arduino Flash Lights, Read Buttons, and do many of the things that you can do with the the regular Arduino environment.
So if you like Scratch and Arduino but are not quite ready for C programming (yet), this is something you can try out.