Who knew ed.gov has a ton of resources. I've always assumed the federal government had to have teaching resources considering they are constantly sticking their noses in to the business of the states but, it's not very well advertised.
free.ed.gov is a collection of teacher resources organized by subject and resource (animations, primary sources, photos and videos). They also have a what's new section which is great if this is a resource that you continue to use.
Check out Our Documents in the primary document section. It's a page dedicated to teaching with the "100 milestone documents" as a way to teach American history. FedFlix in the videos section is another amazing resource; a collection of videos produced by the federal government covering a huge range of topics.
There are many more I could list here but best to explore for yourself and see what would be best to use in your own classroom.