I do a lot of Preview/View/Review in my U.S. History classes — give a preview of the content in Spanish, then have the primary lesson in English, followed by a short review in Spanish. I use many of the resources in The Best Multilingual & Bilingual Sites For Math, Social Studies, & Science for the “preview” part of that sequence, as well as provide those resources for students and their parents to review at home.
Here are new additions to that list:
utubersidad has many Spanish-language videos in history and in other content areas.
Mundo from the BBC also has many resources in Spanish.
Also, searching for “history channel en español documentales” on YouTube generates many results, as does searching for “bbc en español documentales.”