Triangular and perspective grid creation extensions for inkscape
Copy the *.inx and *.py files in to your Inkscape extensions directory (usually ~/.configure/inkscape/extensions). The actual directory can be found under Preferences/System/User preferences.
Note: on my Mac (OSX Mountain Lion 10.8.5) the Inkscape extensions directory is ~/.config/inkscape/extensions
The grids will be available under Effects/Render.
All code is offered under GNU GPL 3 or any later version.