YouTube is a wonderful place to search for resources. There are many great content providers on YouTube that range from enthusiastic amateurs to professional companies that have whole production teams and content researchers.
Whatever your teaching, chances are there is a YouTube video on it.
Sometimes I show the whole clip other times I only show a portion. Below is a list of the YouTube channels that I find useful in my everyday teaching of Science.
"Crash Course is one of the best ways to educate yourself, your classmates, and your family on YouTube!
From courses like Astronomy to US History and Anatomy & Physiology it's got you covered with an awesome variety of AP high school curriculum topics. With various witty hosts at your service, you won't even notice you're getting smarter."
VERITASIUM - Derek Muller
"Veritasium is a channel of science and engineering videos featuring experiments, expert interviews, cool demos, and discussions with the public about everything science."
pERIODIC TABLE VIDEOS
"The Periodic Table of Videos is a series of videos about all the elements on the periodic table, plus other videos about chemistry. We perform experiments, tell amazing stories and go on road trips to places which are chemically significant!"