Photoshop (and Elements) has a terrific filter called Dust and Scratches. It looks for dots and curves on the image that are clearly noise, then removes them. This comes from dust on your lenses or on the photos you’re scanning, etc. An invaluable tool for all image cleanup work.
No such thing in the Gimp world. Search for gimp + dust + scratches and you either find the despeckle filter (which is useless, ime), or references to some 3rd-party plugin which was never compiled for windows.
The best tool I know of comes from the G’MIC plugin for Gimp. This is a must-have tool for many reasons (e.g., making lady’s portrait skin look soft and smooth), but the Remove Hot pixels option under the Repair subset is essentially the same thing as the Dust and Scratches of Photoshop.
I have not read the technical documentation, but the controls are simple: Mask size is the number of pixels at which to consider something being a “hot pixel”. Too low and you miss pixels. Too high and you lose detail in the image. Threshold is the amount of difference to require for something to be considered “hot”. Too high and you won’t change anything. Too low and you change too much. A standard approach is to start with mask size and threshold at minimum, then increase mask size until you fix all/most of the errors, then increase threshold until you stop screwing up everything else. Tip: As this is a compromise, leave the big scratches for manual work: Use the Clone and Healing tools instead.
Here is an example of a BEFORE ==> AFTER.
UPDATE: January 2016
As of the latest G’MIC plugin for Gimp, this effect has been moved to “Repair -> Remove hot pixels”
Also, try the “Repair -> Iain’s noise reduction”
