There are so many. It is important to know what your platform would be and primary use. My preference is Paint Shop Pro. I have used this for so many years. Other option would be google’s Picasa which is very friendly to use and great for most photo editing. If you are on Mac, they have iPhoto that comes with the OS.
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If you ever what to get a job as a retoucher or photo editor - learn Photoshop. It is the industry standard. It is an incredibly capable application that can do or create ANYTHING you can imagine.

It also takes TIME, DEDICATION and PRACTICE to learn it but you will be WELL REWARDED by doing so.

Graphic design courses spend 10 WEEKS just on Photoshop.

Get yourself a book like
Photoshop WOW or
Photoshop for Dummies or
Commercial Photoshop by Bert Monroy

and practice, practice, practice.

There are also a LOT of tutorials on Youtube for how to do stuff in Photoshop.
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I use CS3

As others have said, Photoshop is powerful, complex and expensive. You may want to look at Adobe Photoshop Elements. It’s essentially Photoshop Lite, designed for the home user. It’s less powerful but also more user friendly, and it’s less than $100.
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