There are lots of programs to post process, but they mostly use the same basic set of tools, so instructions for one application are usually transferrable to other applications (though with different menu/keyboard commands). The posts below give some guidance on what you can expect your software to be able to do for you. Many of the examples are based on Photoshop, but if you use something else, you should be able to find the equivalent functions if you browse the menu system or chase the keywords in the software manuals/web guides.