Do you know other good places to sell articles? Every now and then I come up with what I think is a nice easy to understand explanation of something and I'd lo

Do you know other good places to sell articles? Every now and then I come up with what I think is a nice easy to understand explanation of something and I'd love to write it up and sell it. Wouldn't need to be for a lot of money, but if I could make a decent amount to cover some expenses it would be nice. Usually the topic are in math, statistics or philosophy. Nothing a professional (or smart undergrad) on these topics wouldn't already get, but something for other interested people.