This guy wasn't a motivational speaker, but I always got a lot of value from comedian Bill Hicks. Also, David Icke from England is a bit controversial, but has some great ideas. Both can be seen on Youtube if you wish. Also, Michael Tsarion has some pretty crazy and cool stuff you could watch, but he's not motivational, really.
Motivational speakers and writing is like a drug. Just don't get addicted to them. Although the side effects can be positive, just remember to use your common sense when listening to people speak. Some of the people out there turn out to be complete frauds who give bad advice. Just let your intuition be your guide.