I havent had the chance to hear Will Keim speak, but another awesome speaker is Mike Green aka "Greenie".
Green is a recovering alcoholic who goes around talking about his experiences, those of people who he coached on sports teams and coahes he knows and also of Greeks. Ive seen him twice and would see him again. He hands does a survey of the room to see how often people drink and other activities. You would never believe how many hands shoot up and how everyone looks around the room in amazement because everyone is pretty much a "One Night Stand". Which means because of the way you drink, there will be one night that you do or have done something that you will regret, even if you're just a social drinker.
It's a talk primarily for Greeks and athletes but the student body is always welcomed and he always has a full room. In fact he is so good that Panhel and IFC made it mandatory for all new members to see him. If not there was a penalty (unless you had class or something you couldnt get out), but he's worth seeing. I recommend him to any Greek Council and college student bodies in general.