I've started walking to work again, and I love it! I bought some cheap but comfy walking shoes so I don't have to factor in footwear every morning. I love the fresh air and additional exercise. If I walk home for lunch, which I usually do, my walking totals 32 minutes. And I'm saving on gas. My savings will add up if the price of gas keeps climbing.
One of my favorite things about living in Europe was walking everywhere, and I'm glad to have it back in my life. If you live close enough to work to walk or ride your bike, I suggest you give it a try.