From (updated 2010)
Is it illegal to drive without shoes? - DMV Answers
Traffic Laws Regulating Shoes
This is one of the few traffic laws every state agrees upon. Shoes are not required to operate a vehicle. Every state permits barefoot driving. There are no laws or ordinances prohibiting hitting the gas and brake pedals with naked feet, resulting, if caught, in a traffic ticket and/or citation.
The closest law prohibiting barefoot driving comes from Alabama, which states: "Operation of a motor vehicle by a driver with bare feet is permitted. Exception: motorcycle rider."
Lawmakers in Ohio, Wyoming, Missouri, Iowa, and Indiana allow barefoot driving but recommend against it, citing this practice as unsafe, a car crash waiting to happen.
The choice is yours. Drive however you see fit. As long as you practice safe driving habits, it does not matter if you're wearing shoes, flip-flops, or going barefoot.