Here is an example of how cropping a photo completely changes it's appearance and enhances the end result.
This photo is uncropped... But it is thrown off by the window to the right, as well it is not straight.
So I used ACDSee and made the photo right by cropping and getting rid of the window.
Cropping is great to get rid of distracting elements in a photo. Because you are making the visual judgement your crop is still your work.
I find it hard to take good photos with a point and shoot camera because I can't use the viewfinder and I need to have no sunlight to see my screen. This way I can take bad images and make them better.
Here are two other examples:
The above image is distracting because of the uneven line at the top left. So I cropped it out and below is the result.
I also took a picture of a tree that was rather uninteresting so I added more colour and contrast and cropped a landscape photo to portrait.
This is the before, nice tree but nothing interesting.
This is after and as you can see i fixed up the colours and the composition is more appealing.
The program I use is called ACDSee as mentioned before and is one of my favorite programs for photo editing.