Crash Course Kids is a perfect supplement to use in science for upper elementary/intermediate grade students. I plan to share these videos with our science department.
I checked out this site by recommendation from someone on the Future Librarians Facebook page and was amazed by how well materials were organized for teachers and are so user-friendly for students. I love the quests for the students and I think the printable certificates and badges are perfect! Lessons are intended for students in grades 5-9 and are ISTE aligned and free for use under Creative Commons license. I may be the last person to know about this site, but I can't tell you how glad I was to find it!