TED's web site is full of presentations, from 4-20 minutes long, covering countless topics.
Some are funny, some are thought provoking, some are inspiring, and some are all 3.
Type a topic you are interested in, from television to ocean animals to government, into the search box, and see what comes up! (One of my favorites is about "underwater astonishments" by David Gallo. Only 5 minutes long, and DEFINITELY worth the time!)