This site has quite a few free math learning resources. There are interactive lessons, printable worksheets and a worksheet generator, a few simple flash-based games, some webquests on fun math topics, and more. It's a no-frills website, that's not terribly interesting visually, but there are plenty of useful tools to explore.
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.