Numberphile — interesting and/or quirky mathematical concepts presented in an engaging and accessible manner by well-established mathematicians.
Plus Magazine — a very readable yet informative magazine for anyone interested in maths. There are articles, news of latest research, interviews, puzzles, and more!
Chalkdust Magazine — “a magazine for the mathematically curious” is their tagline. It is perhaps more friendly to the general public than Plus Mag, but that doesn’t mean it’s light on mathematical content.
VSauce — one of the most popular educational YouTube channels. The topics presented and questions raised often involve a fascinating combination of scientific and philosophical inquiry.
Tom Scott — his Twitter profile says “I make things”. You’ll find short videos on a bewildering range of topics, touching on history, geography, politics, language and linguistics, computer programming, physics, popular culture and society, and more!