Scratch is a high-level block-based visual programming language and website aimed primarily at children as an educational tool, with a target audience of ages 8 to 16.
ScratchJr is a visual programming language designed to introduce programming skills to children ages 5–7. The app is considered an introductory programming language.
Code.org is a great resource for all types of CS ideas. Ideas like "hour of code", and "unplugged" activities are easy to find here, and you can filter ideas by grade level and other ways.
The National Center for Computer Science Education is housed at The College of St. Scholastica. The Center champions, researches and provides equitable computer science education opportunities for K-16 students and educators.
CS First is offered through Google and offers lesson plans and curriculum ideas that you can filter by subject and grade level.
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.