GIMP Plugin Registry

The range selection script is a tool for easy and automatic creation of selections and lay­er masks. The selections or masks include all parts of the image that are situated within a defined range of tonal values, colours, saturation or edges. Selections can be based on one of 16 channels. For detailed instructions and several samples have a look at the attached manual.

This plug-in changes colors in an image based on the HSV difference between two colors. This is particularly useful for applying color themes to existing images.
It avoids burning out high saturation and value at the expense of compression them somewhat when the difference goes towards higher saturation and value.
Current bugs/missing features include:
Undo does not work.
It can't be used on indexed images, even though it would frequently have enough colors.  read more »

Saturation Fix for restoring clipped colour channels.

Guide to Using the Saturation Fix Script

Creates an image of rainbow coloured circles to give a plasma-like pattern. Also comes with an animation script that animates the pattern. Frames are saved as layers. Choose min and max speed and circles are randomly increases/decreased in radius according to the set speeds.
TODO - Save frames as XCF files compatible with GAP.  read more »