A Fortran 90/95 API, which provides routines that enable direct access to gnuplot from within a program. SourceForge page, with project summary, news, and source download.
Interface for ANSI C by Nicolas Devillard. Module enables sending display requests to a Gnuplot session through simple program calls. Includes documentation and downloads.
A Python package, that interfaces to Gnuplot allowing the use of Gnuplot from within Python to plot arrays of data from memory, data files, or mathematical functions.