Inception bears more than a passing resemblance to this Scrooge McDuck comic. You can read it in full at the link. Via.
Calvin and Hobbes also featured multiple layers of dreaming. Via these sites.
Here's a long explanation for why Inception is "about Chris Nolan's anxieties when making a movie, especially one where so much other-peoples-money is at stake."
And here, Inception's costume designer gives strong hints about the plot. Via.
*Buy Inception posters at Amazon.