GIMP Plugin Registry

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