In Autumn 2020 I am teaching Math51 and Math113 at Stanford.
Below is a list of resources intended to help students interested in mathematics and STEM find and explore communities, ideas, mentors, and research opportunities. The resources should be used only as a guide: this is, of course, an incomplete collection, and I don't have first-hand experience with many of the people and organizations listed. Please email me with suggestions to add (or subtract) to this list! Items are currently US-based, but only because that is the region I am most familiar with.