From the OpenScad mail list
"it is possible to use an
external editor by opening the file in both OpenSCAD, File->Open, and in your editor, vi xxx,
and then enabling Design->Automatic Reload and Compile in OpenSCAD. It seems that every time you write the file from within your editor OpenSCAD will see the change, reload the file, compile
it and show the results in its render window. It cleans things up a bit if you View->Hide Editor."
Just tried it out on windows and Linux and it works great in a variety of editors. Lets you have a full screen for the render window and use you favorite editor.