This site has many simulations helpful in understanding various computer science topics taught in high school.
The index has a list of all the topics taught on this site.
Some favorites:
It is a website with hip hop videos and instructional activities that promote literacy and spark creativity. This could be used as a Friday fun activity. Students have fun while learning and mastering a concept.
It is a website that has a paid subscription
Erase All Kittens teaches children to code in a completely new way. Instead of just learning simple concepts, kids can learn professional languages by changing the code of the game, in order to build and fix levels as they play.
An online interactive resource for high school students learning about computer science.
Open source
This project is completely open source and available on GitHub.
CS Unplugged is a collection of free teaching material that teaches Computer Science through engaging games and puzzles that use cards, string, crayons and lots of running around.
Printables
This page diplays a complete list of all available printables. If a lesson uses a printable, the lesson will contain a direct link to the printable with a description on how to use it.