Jason Fried:
When you make something you make something else. Just like they say you can not not communicate, you can not not make something else. Everything has a by-product. Observant and creative entrepreneurs spot these by-products and see opportunities.
This is exactly how Delight is in the Details came to be. It started as a topic for several episodes of my members-only podcast, and then I picked it up and turned it into something so much more.