The video below by Vi Hart celebrates how the concepts of mathematics such as angles, rotation, prime factorization, and symmetry are used to create beautiful patterns of snowflakes, starflakes, and swirlflakes.
All in all site has a collection of more than 12,000 videos that cover a variety of topics aside from those mentioned above. The collection includes other sciences such as Physics, Engineering, Astronomy, and Computer Science. Social Sciences videos are also available.
In addition to the 5000 videos that I have shared to you last year, I have recently discovered more than 1500 links to mathematics video lectures in Pinterest. The links cover a wide variety of topics which include K-12 Mathematics, Math Interviews and Humor, Famous Mathematicians, Student Lectures, and many more.
The collection also includes undergraduate and graduate content topics such as Abstract Algebra, Graph Theory, Topology, Number Theory, Optimization, etc.