Reuters just released it guidelines for using Photoshop.  Some very interesting
rules are set down for their photographers.

ALLOWED:

• Cropping
• Adjustment of Levels to histogram limits
• Minor colour correction
• Sharpening at 300%, 0.3, 0
• Careful use of lasso tool
• Subtle use of burn tool
• Adjustment of highlights and shadows
• Eye dropper to check/set gray 

NOT ALLOWED:

• Additions or deletions to image
• Cloning & Healing tool (except dust)
• Airbrush, brush, paint
• Selective area sharpening
• Excessive lightening/darkening
• Excessive colour tone change
• Auto levels
• Blurring
• Eraser tool
• Quick Mask
• In-camera sharpening
• In-camera saturation styles

Click here to see all the guidelines and an explanation of the rules.