Some personal favorites:
Bryan Stevenson, Human Rights Lawyer: http://www.ted.com/talks/lang/en/bryan_stevenson_we_need_to_talk_about_an_injustice.html
Brene Brown, social worker, researcher: http://www.ted.com/talks/brene_brown_on_vulnerability.html
Dan Ariely, behavioral economist: http://www.ted.com/talks/lang/en/dan_ariely_on_our_buggy_moral_code.html and, if you’d like to see more from his work, http://www.ted.com/talks/lang/en/dan_ariely_asks_are_we_in_control_of_our_own_decisions.html
Ben Dunlap, President of Wofford College: http://www.ted.com/talks/lang/en/ben_dunlap_talks_about_a_passionate_life.html
Shawn Achor, positive psychology: http://www.ted.com/talks/shawn_achor_the_happy_secret_to_better_work.html
Hans Rosling, statistician: http://www.ted.com/talks/hans_rosling_shows_the_best_stats_you_ve_ever_seen.html (he also has many other TED talks well worth the time)
Vilayanur Ramachandran, UCSD neuroscientist: http://www.ted.com/talks/vilayanur_ramachandran_on_your_mind.html
Simon Sinek, Author and Lecturer on Leadership: http://www.ted.com/talks/simon_sinek_how_great_leaders_inspire_action.html
Pattie Maes and Pranav Mistry, engineers: http://www.ted.com/talks/lang/en/pattie_maes_demos_the_sixth_sense.html, with more here: http://www.ted.com/talks/lang/en/pranav_mistry_the_thrilling_potential_of_sixthsense_technology.html