bigFORTH is a native code Forth written by BerndPaysan. It is available for Linux and Windows 95/98/NT under GPL. The most striking feature is the graphical user interface MINOS and the form editor Theseus (MINOS and Theseus are still beta).
More about bigFORTH can be found at http://www.jwdt.com/~paysan/bigforth.html
Some samples of the graphical features provided by MINOS:
The Theseus form editor:
