Imagej (http://rsbweb.nih.gov/ij/) has an awesome feature that allows you to perform an FFT on an image, edit it, and then do an inverse FFT. This is very useful for eliminating patterns from an image, such as the texture of old photographs.
Full size images for further comparison:
http://www.flickr.com/photos/ftzdomino/4065410668/sizes/o/
http://www.flickr.com/photos/ftzdomino/4064662889/sizes/o/
