A free cross-platform library of fast C++ routines for the plotting of up to 3-ranged data. It can export to bitmap and vector EPS/SVG files. There are window interfaces (GLUT/FLTK/Qt) and console tools. MathGL can be used from C/Fortran/Python/Octav/Lua
QNANWidgets is a collection of science/engineering oriented Qt Widgets to help in creating sci/eng. applications and include a chart and plot widget. The widgets are easy to use and can be customized in Qt Designer directly.