Does anyone remember the Dataflow-Language ProGraph? The one where you just wired boxes together but didn't write normal code? The one where Spaghetti-Code still consisted of real twisted bands? There was once a version for the old, classic Mac OS.
Now there is a version from Andescotia Software for Mac OS X. At 60 dollars maybe not exactly a bargain for an obscure piece of programming language history, but somehow I still like it. Let's see if I have money for it.
If you want to see ProGraph in action, there is a quite usable tutorial online. And of course, there is a bit about the history and development on Wikipedia.
Addendum: of course I have the money. Was to be expected. A bit slow, the download, but it runs.
The open-source approaches are, by the way, quite emaciated so far - and on the websites to a larger extent consist of complaining, whining, and confusion.