Working at a small private school, I need to be creative with my budget. Many schools can just buy licenses for all the software that they need. I do not have that option. I am constantly seeking free or open source alternatives to the standard software being used in schools. Most people are aware of Open Office as an alternative to Microsoft Office. Some people are familiar with Gimp as an alternative to Adobe Photoshop. Now if you are a power user these alternatives may still be lacking, but for the average user they are excellent options. To find alternatives to many of the programs that you use daily you should use one of the following sites:
Alternativeto.net
My first choice for finding alternatives to both desktop and mobile applications.
Osalt.com
Another site where you can search for alternative software.