Today's software is GeoGebra. It's a collection of free software and online math tools for Graphing Calculator, Geometry, 3D Graphing, Augmented Reality, Graphing, Spreadsheet, Probability, CAS (A software program that facilitates symbolic mathematics - Yes, I had to look it up.).
I was amazed by everything that you can download and do at the website. All of it for free. There are lesson plans for teachers from Elementary grade level to College Prep and College level. There are fun exercises.
The FAQs, User Help and User Forum are all up-to-date, easy to navigate, and well done. As a person who deals with a lot of Linux software sites, I was incredibly jealous of their FAQs and User Help. If GIMP was that organized Photoshop would be out of business.
Go to the GeoGebra website or click on the FB link and check them out. You will be amazed at what they have available for free.