As someone who can be a little clumsy in heels, flats are a natural choice for me. I recently heard someone ask whether or not flats are professional / dressy enough to wear to work. My answer was a very loud and excited "Yes!"
DV by Dolce Vita, White Leather 'Savannah' Cap Toe Flats, $46.20 from Bluefly. These shoes are so classic, how could you not wear them to work?