Take your pick from:
-photo enhancement tools;
-image/database catalog for Windows or for Mac;
-photo album creation and special effects;
-photo art and effects;
-organize/fix/share for Win and Mac;
-stitching and panorama tools;
-JPEG tools and so on.
We can also classify digital photography software into beginner and advanced photo editing tools. Image editing is considered highly important if we think that the images need to be cleaned up a bit before being used. This is not a must-follow step when you take amateurish photos, however, for hobbyists and professionals, the requirements are higher.
A basic digital photography software includes some standard features that enable the user to rotate, sharpen and crop the photos. You can check the list of free tools available online, and see whether any of them would work for you. Pay attention to get a program that has simple to use menus and wizards because you don't want to put too much time into photo editing. It may be a big waste for you.
Corel Painter and Adobe Photoshop CS are professional photo editing tools. They offer the kind of digital photography software features that are available only with high-end programs. You won't get the features in these two when downdloading some lower-end package. Do your research well before paying for such a program, as it doesn't come cheap. Clearly evaluate your needs, because it is best on them that you should shop around.
A rather new class of digital photography software has gained importance over the last years: photo management programs. Such tools are designed to help you better organize the photo collection and create the kind of albums and files you need. The Adobe Photoshop Album 2.0 deserves mentioning here because it has a very clean user interface and it is highly attractive. ACDSee works fine too and so does Unlead Photo Explorer.
Have a look online, and go through the software lists available with reliable websites. The data there is convincing.