Vilayanur Ramachandran studies the brain. You may have seen a profile of him in last month's New Yorker...if you haven't get thee to a library and check it out! Anyway, Ramachandran is an interesting speaker -- he spends a lot of time dealing with bizarre neurological problems (not his own, of course), and he makes neurology sound downright fascinating. Have a look at this TED Talk from 2007 in which he describes several puzzling neurological syndromes.
Discussed: how brain damage is very selective, mapping function to structure, capgras syndrome (face blindness), the capgras delusion (in which patients believes that their friends and family are bodysnatcher-style imposters), some digs at Freudians, phantom limb syndrome, the now-famous mirror box, phantom fingers on the shoulder (!), synesthesia, kiki and boobah.