TED.com (Technology, Entertainment, Design) is a very popular website that has videos on just about any topic you can think of. There is also a spin-off to the TED website called TED-Ed. TED-Ed is going to be geared more toward older students, depending on the topic. This website http://ed.ted.com is a website that has video lessons on different educational topics such as Algebra, Art, etc. You can also adapt and edit any lesson featured on TED-ED or create lessons around any YouTube video.