Math education! Anything math related that is useful for education, teachers, or students. There should be an emphasis on usefulness (such as good internet resources or ideas for how to teach a concept). Note: This is not a subreddit to publicize each post in your (or any single) blog or website, but rather to point out resources you've found that you could actually see bringing something useful to a math class.
The aim of /r/Physics is to build a subreddit frequented by physicists, scientists, and those with a passion for physics. Papers from physics journals (free or otherwise) are encouraged. Posts should be pertinent, meme-free, and generate a discussion about physics. Please report trolls and intentionally misleading comments.
Cryptography is the art of creating mathematical assurances for who can do what with data, including but not limited the classical example of encrypting messages so that only the key-holder can read it. Cryptography lives at an intersection of math, programming, and computer science. This subreddit covers the theory and practice of modern and *strong* cryptography, and it is a technical subreddit focused on the algorithms and implementations of cryptography.
DepthHub gathers the best in-depth submissions and discussion on Reddit. You can use [the DepthHub](http://www.reddit.com/user/Lapper/m/depthhub) as an alternative front page with high quality discussion and inquiry. For more on the theory of DepthHub, [read this post from our founder](http://redd.it/bkd0n).
A subreddit for really great, insightful articles and discussion. Please follow reddiquette, and READ THE ARTICLE before voting or discussing. Downvotes should only be used if something doesn’t contribute to intelligent discussion, not just because you disagree. Please use the report button if you see something that doesn’t belong.