Several graphical user interfaces have been written for `gnuplot` and one for win32 is included in this distribution. In addition, there is a Macintosh interface (broken link).
Also several X11 interfaces exist. One of them is called xgfe, it uses the Qt library (broken link)
In addition three Tcl/Tk located at the usual Tcl/Tk repositories exist.
Bruce Ravel (ravel@phys.washington.edu) has written a new version of gnuplot-mode for GNU emacs and XEmacs. This version is based on the gnuplot.el file by Gershon Elber. While the gnuplot CVS repository has its own copy the most recent version of this package is available from http://feff.phys.washington.edu/~ravel/software/gnuplot-mode/