TED is a global set conferences which started in 1984 dedicated to disseminate “ideas worth spreading.” TED which stands for Technology, Entertainment and Design is owned by Sapling Foundation, a private non-profit organization.
Now, what might interest you about TED are the free videos, many of which are lectures about mathematics and technology. The video above is the lecture of famous mathematician Benoit Mandelbrot about the beauty and complexity of fractals. Most of these TED videos have transcripts that are also available for download.
As of this writing, there are more than 900 TED videos or TedTalks in science, technology, entertainment, design, business, and global issues. These videos are under Creative Commons License, so you are allowed to repost and share them.