Here's what they say about doodles: "Certain types of doodles are in higher demand than others, like map icons, hipster coffee-ware, and hand-drawn fonts. Think about what you could create and sell on your own, just by taking your everyday doodles one step further. You don’t have to go after every single corner of the market, but chances are there’s someone who needs illustrations of something you really love to draw."
Check out the complete post for more inspiration and start putting those doodles to work. And don't forget to explore the other interesting articles on their blog.