"Read, every day, something no one else is reading. Think, every day, something no one else is thinking. Do, every day, something no one else would be silly enough to do. It is bad for the mind to be always part of unanimity". -Christopher Morley
Sound advice for any planner -curiosity and an awareness of different perspectives are our stock in trade, and you ain't gonna find new pearls within your regular daily routine.
Read a specialist magazine from a field you know nothing about.
Visit some random blogs (try stumbleupon).
Try a new cafe and eavesdrop on people.
Take a different route home.
Eat new foods.
Imagine how someone else (a boatbuilder, an ant, a drummer) would attack your problem.
(photo credit: Scott)