Here are some things I've done to popularize mathematics. For popular/recreational mathematics created by others, check out my LINKS page.
I recently made a YouTube channel with an aim to create fun, animated videos about interesting topics in maths. Here's the first one, and stay tuned for more.
A híres Riemann-sejtés (The famous Riemann Conjecture), Egyetemi Tavasz, (Szeged, Hungary, Apr 18, 2015).
V-E+F=2, TUDOD? Award Ceremony, (Szeged, Hungary, Mar 1, 2016).
Hogyan (ne) tévedjünk (How (not) to be wrong), Eötvös-Esték, (Szeged, Hungary, Apr 4, 2017).
A változatlan (The unchanging), Egyetemi Tavasz, (Szeged, Hungary, Apr 22, 2017).
Hogyan (ne) tévedjünk (How (not) to be wrong), HÍD-camp, (Szeged, Hungary, Jul 12, 2017).
Two riddles and linear algebra, iNIGMA 'Seminários Diagonais' (Porto, Portugal, Nov 2, 2017).
TUDOD? is a Hungarian website of riddles I created with the help of a few of my collegues at the University of Szeged in 2016. You get one riddle at a time, usually in the form of a picture, to which the answer is either a positive integer or a single lowercase word. All riddles are connected to higher-level mathematics, which you don't need to know for solving them, but you'll be guided to find out more about it once you did. You can also get 3 hints for each riddle if you get stuck, but your first hint is always the title.
The riddles where originally intended for students of University of Szeged, however anyone can go ahead and try them. If you don't speak Hungarian, consider that as an extra challenge :) Google translate or a dictonary will help you out. There are some puzzles where knowing some undergrad mathematics helps.