Enhancer is a plug-in for leading photo editors. I used it with Macromedia Fireworks, which it was added to the Filters menu.
Enhancer detects underexposed, overexposed and mid tone areas of a photo, but does not change overall exposure.
The before picture below has a "messy" background that detracts from the butterfly.

When I open Enhancer, I see my original image.

There are three controls I can use to immediately see what changes occur in my image.
Fiddle with the sliding controls until I got the image below - a distinct improvement over my original photo.
I see the effects of my changes in the After tab. I can click back to the Before image at any time.

AKVIS Enhancer intensifies color transition: strengthens the difference between adjacent pixels, and reveals not only details in the shadow but details in the overexposed and mid tone areas, as well.
Enhancer has versions for both Windows and Mac.
Download the Windows trial version or the Mac version.
You can get it in several languages (English, German, French, Spanish, Russian, Italian, Portuguese, Japanese), with Help files in most of these languages.
There are three versions: home ($68), commercial ($79), and educational (email for pricing to sales@akvis.com.)
Of course, it is best if you get a good exposure, the right depth-of-field, and good lighting when you take a picture. But since this is easier said than done, Enhancer can come to the rescue.