This is a script that is based on the lightning tutorial (http://gug.sunsite.dk/tutorials/tomcat9/). It was tested on GIMP 2.4 (so, using the new scheme engine).
It comes with two versions; one that creates an image of lightning and another that creates an animation (using layers as frames) of lightning with parameters to modify the turbulence so the lightning bolt appears to dissipate over time.
Pandora simplifies the process of stitching together a sequence of panorama images.
Load all the panorama pieces (in order) as layers inside an image (suggestion: make a new image then "Open as Layers" and select all the files). Then run Filters->Combine->Make Panorama.
You still have to do the detailed matching by hand, but Pandora calculates the needed image size, moves all the layers to approximately the right position and creates appropriate layer masks for fading each image into the next.
TESEO2: Turn the Eldest Seismograms in the Electronic Original Ones Teseo2 has been developed for quick and accurate digitisation of historical seismograms from raster files, introducing a vectorisation step based on piecewise cubic Bezier curves. The vectoriser can handle greyscale images stored in a suitable file format and it offers three concurrent vectorisation methods: manual, automatic by colour selection, and automatic by neural networks. Teseo2 is developed in respect to the "Open-Source" philosophy and it is freely distributed under GPL license.
Plugin to load Photoshop ABR brushes as image in GIMP. Multiple brushes included in a file are loaded as layers. Should handle v1, v2, v6.1 and v6.2 sample brushes (though I don't known which PS release create each). Requires Gimp 2.4.