GIMP Plugin Registry

Easily map colours from a source colour to a target colour. Very effective for matching skin tones across images or between people.

Relatively quick (but not earth shattering). It doesn't work with grayscale or indexed images. Has preview, works with selections and layers, etc. Very, easy to use, and quite useful for portraits or recolouring graphics.

A demonstration: Lenna's face is mapped to the colour of the feather on her hat. This was done by selecting a colour from her face, then selecting a colour from the feather.  read more »

This Shadow&Highlight script does a decent job of lightening shadows and/or darken highlights in photographs. The UI gives you five control sliders. Two for control of the Shadow and Highlight amount (opacity), two for the tonal width of each contrast mask layer (using gamma), and one for the blur radius of the masks. Plus the option to flatten visible layers when done.  read more »

Adds a Contrast Adjustment layer to your image to help fix contrast problems.

Guide to Using the Contrast Fix Script