This is a list of the projects that work with octave in some way. It is not yet a comprehensive list, but it should give an idea of what is available.
Octave Forge
octave.sourceforge.net Current version 2006-03-17 for 2.1.72
This is intended to be a central location for custom scripts, functions and extensions for GNU Octave.
Plotting Projects
Octaviz
octaviz.sourceforge.net Current version 0.4.0
Octaviz is a visualization system for Octave. It is a wrapper that makes all VTK classes accessible from within Octave using the same object-oriented syntax as in C++ or Python. Octaviz also provides high-level functions for 2D and 3D visualization. Using those functions, most common visualization tasks (3D surface plots, contour plots, meshes etc) can be accomplished without any knowledge about VTK.
Octplot
octplot.sourceforge.net Current version 0.3.5
OctPlot is a handle graphics package for Octave. OctPlot provides quality postscript(TM) and screen graphics. OctPlot is free open source software under the terms of the GNU General Public License (GPL).
OctPlot should run on following systems: Cygwin (MS Windows), Linux (and possibly other UNIXs), OS X
Graphical User Interfaces
Octave Workshop
www.math.mcgill.ca/loisel/octave-workshop/ Current version 0.10
A GUI implementation for Octave that has the goal of being completely cross platform (the initial and the development platform is Windows with MingW).