A Quick and Effective Way to Enhance Contrast in Photoshop
http://digital-photography-school.com/a-quick-and-effective-way-to-enhance-contrast-in-photoshop
How to Effectively Use Contrast, Auto Levels, and Batch Processing - Psdtuts+
http://psd.tutsplus.com/tutorials/photo-effects-tutorials/how-to-effectively-use-contrast-auto-levels-and-batch-processing/
Diffen - Compare Anything. Diffen. Discern. Decide.
http://www.diffen.com/
The Principle of Contrast in Web Design | Tips
http://webdesignledger.com/tips/the-principle-of-contrast-in-web-design

The Principle of Contrast in Web Design | Tips - http://webdesignledger.com/tips/the-principle-of-contrast-in-web-design