This company carries textbooks, workbooks and ebooks in all major subjects. They are advertised as "resources for struggling learners" so many of the books are high interest/low reading level. There are some useful life skills resources as well. Prices are pretty reasonable.
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.