This site has a collection of over 500 science lesson plans for grades 5 through 12. There is also a smaller selection of kid's experiments. There's a good search function, so you should be able to find what you're looking for, and all resources are free.
Saturday Grab Bag
Printable curriculum materials for preschool through second grade levels.
Thursday History/Social Studies
This website from the Government Publishing Office has resources for learning about the US govern
The name of this site says it all!
Tuesday Language Arts
This company provides programs for beginning reading and math learning.
This company publishes three books for helping elementary learners explore science.
Self-paced, online courses for learning coding.