Useful Websites for Teaching

As an educators we are always looking for good info to use in our classes. Sometimes we create our own lessons, or sometimes we use others --for example-- videos prepared for others teachers or organizations. I believe that a good teacher should be able to look for the resources he/she needs as well as create her/his own. For example for videos you can go to: http://www.teachertube.com http://youtube.com https://www.teachingchannel.org/ https://www.khanacademy.org/ There are so many websites, and depending on the topic, teachers should find the ones are useful for their classes. You can google them, ask them or use your favorite search engine. Which ones are your favorities?