I was glad to be interviewed by DZone a while ago. The second interview was on my current Open Source work and I gave what is probably a non-traditional answer on why Open Source contribution is important for a developer. The google appengine project I'm talking about is the qrcode linkulator. And, for the record, I've got a better hair-cut now.
My statistics are from this article on Functional Fixedness at wikipedia. The over-lapping concept I'm trying to tease out is that there are problem solving exercises that are not served by tightly focused environments like business. As a developer you need to be able to work in spaces that allow for creative freedom and the lessons you learn there (for better or worse) translate back into your "high pressure" environment. The result is a better developer that is able to think outside the parameters of the problem.
A nice animation covering the idea popularized by Daniel Pink (who is an infinitely better speaker) is on youtube:
My contribution is: not only is open source a product of intrinsic motivation... it creates intrinsic motivation to improve yourself as a developer. These improvements translate back to your "day job" ... so for purely selfish reasons you *should* create open source code. You will be forced to learn. You'll get interaction with other developers. You'll learn much more than if you stay locked in your office and never get challenged by people who never would think like you do and have no reason to pretend they do.
Even if the project is a failure and your contributions are insignificant... you'll learn something.