You may know John Cleese as one of the iconic creativity minds behind Monty Python, or as an actor in films like Die Another Day (he played Q?), The World Is Not Enough (he played R), two of the Harry Potter Films (who could forget Nearly Headless Nick), or The Great Muppet Caper. Seriously he's done some memorable films as well, including Rat Race - one of my all-time favoriate comedies.
The man is also a productivity genius, giving thoughtful and compelling interviews down through the years as well as lecturing on creativity. The talk below I especially love because he goes into detail on how your mind keeps chewing on a problem even while you are sleeping.
I have found it very powerful to take a hard problem I'm stuck on, sleep on it, and see if it is still really such a problem the next day.