This site aims to provide an uncommonly inviting place to teach and be taught. Instructors can upload video on any subject, then divvy it up into lessons. Unlike YouTube, Curious lets teachers choose to charge for lessons, features an oversize playback window and generally feels friendly and constructive. There are no creepy comments from anonymous YouTubers here, and the site’s proprietors currently approve teachers and eyeball content to ensure that these online classes are, well, classy.