TED is a great source for researchers and lecturers alike. It seeks to “make the best talks and performances from TED and partners available to the world, for free” (www.ted.com). By now, more than 1400 talks are available online for streaming or downloading, all of them subtitled in English and many of them in other languages as well.
This is how TED explains their mission:
We believe passionately in the power of ideas to change attitudes, lives and ultimately, the world. So we’re building here a clearinghouse that offers free knowledge and inspiration from the world’s most inspired thinkers, and also a community of curious souls to engage with ideas and each other.
Only few of the talks explicitly address issues of sustainability, but those who do are highly recommended: If you are familiar with the concept of “planetary boundaries” by Johan Rockström and colleagues, I am sure you will love his inspiring 2010 talk here. Or how wold it be if you get Al Gore to give a guest lecture in your classroom? Beside, there are many other topics that are not linked directly to sustainability but might be of interest as well: cocial innovation, gender issues, intercultural communication and many more.
The website is a great source for discovery of good talks with quite a few I already used in my teaching and students loved them. They also come in handy for other presentations, so I recommend you give it a try!