Flow is a drag-and-drop (prototype) dataflow programming environment for the Arduino. It is built on the Plumbing libraries for occam-pi, and executes on the Transterpreter virtual machine.
You can download Flow for Mac, Linux, and Windows. If you have problems, please join the users mailing list at concurrency.cc. (This is a very,very early-stage prototype---you have been warned.)
See the quick getting started documentation that we put together. It's enough for you to get started, we hope. Or, just fiddle.
You can find out more about the underlying tools and technologies at concurrency.cc.
Flow is made available under a GPL v3 license.