Lifehacker points out a simple trick for achieving high contrast photographic magic. Essentially you make a copy of the Green color channel then overlay that on the original picture. Make it slightly transparent and you'll get an effect that ups the detail and contrast at the same time. Check out a step-by-step in the video below.
What color channel wizardry do you rely on?
Note: In Paint.NET you'll find this under the "Adjustments" menu then "Color Accent." Make "Duplicate" layer then select the top layer and open the "Color Accent" tool. Crank "Green" to 100 and click "OK." Then click the "Properties" button for the layer and set it to "Overlay" and slide the transparency to about 50%.