Catch Sick Science videos every Tuesday on YouTube. Sick Science just posted their 100th video last week on Moss Graffiti– see embedded below. The clips typically show you how to set up a science demonstration or investigation and then leave the audience with a question or prompt to respond to in the comments.
These clips seem appropriate for elementary and middle school students. With 100 videos there is a substantial set to search and use for science fair projects or to supplement a concept you are teaching.