A general purpose high-pass filter plugin. It shows up as Filters->Generic->High Pass Filter. You can select a blur radius that sets the size of detail to be passed by the filter, as well as an option to keep the source layer or replace it.
EDIT: Updated to use grain extract rather than the previous method, This looses less histogram data and is closer to the Photoshop version...
It actually implements 5 different high pass modes:
exposure-blend makes quick work of blending 3 bracketed exposures into a detailed, realistic, extended contrast image. It has many features to save you the drudgery of assembling contrast blended stacks yourself:
'watermark' by Doug Reynolds allows the user to add text as a watermark into an image. The watermark text is done as a lighter overlay of the background of the image. Besides the text itself, the user can choose the font from a pull-down menu, size (in pixels), location (one of the four corners), and opacity (in percent).
After installation the plugin script is availbe under the menu: Script-Fu/MyScripts/Watermark.
This program creates stereoscopic 3D anaglyph photos from a stereo pair. In order to make use of this program you will first need a pair of images from slightly different angles or the same object. You then need to place both images as different layers in the same image window in Gimp with the right image as the Bottom layer and the left image as the next layer above it and no other layers in the image (if you use this script in other circumstances then it probably won't work properly).