Modkithttp://www.modk.it/ (http://http://www.modk.it/)
Modkit is an in-browser graphical programming environment for little devices called embedded systems. Modkit can currently program Arduino and Arduino compatible hardware using simple graphical blocks similar to and heavily inspired by the Scratch programming environment developed by the Lifelong Kindergarten Group at the MIT Media Lab.

Arduino in Schools (Visual Programming Options)http://transitlab.org/2010/arduino-in-schools (http://http://transitlab.org/2010/arduino-in-schools)
How to access arduino, a lot of the competitors to arduino have visual programming (for instance Flowal). Here are the three visual programming languages I know of for the arduino.