Before writing this I am assuming that you are aware of TED, and if not you can learn more about TED here and also you can learn more here TED on Wikipedia.
TED has great videos and it would great if you can keep a personal copy, TEDinator allows you download TED videos.
Features:
- Sort download according to title, location, year and month, and play time.
- Download everything one click.
- Freeware.