TED
TED talks are an online video service that have leading experts in many different fields giving short lectures.
The site can be accessed here: http://www.ted.com/#
Since it has so many different ideas presented on it, it is quite easy for a teacher to find a TED talk and use it as a start point for a lecture.
Also, if students use it on their own time, the ideas presented on the site can lead to much more interesting and lively group discussions, and since they are quite fun to watch, they don't really feel like homework. Students with lots of homework could even use them as a break.
Again, there is no age requirement that I have found.
