Consider them for speech classes and also as springboards for writing critiques as well as argumentative and persuasive essays.
The Myth of Violence- http://www.ted.com/talks/steven_pinker_on_the_myth_of_violence.html (look at speaker presentation, visual aids, use of resources, speaker’s purpose and use of proof, etc.)
What’s the Right Thing to do: http://www.ted.com/talks/michael_sandel_what_s_the_right_thing_to_d… (watch how speaker uses a story to begin his speech, polls the audience- pulling them in, moves out from podium)
How Schools kill creativity- http://www.ted.com/talks/ken_robinson_says_schools_kill_creativity…. (notice how speaker uses humor at start, purpose 3:15, uses humor again, gives a story 3:40
How to make a splash- http://www.ted.com/talks/alexis_ohanian_how_to_make_a_splash_in_soc… (show all- notice how he uses visual to enhance his speech)