I'm a lawyer, so I mostly have slacks and a dress shirt, and occasionally have a suit. Mostly my commute is between 3 and 6 miles, so I can wear work clothes (and really, I have to, because I spend a lot of my day going from place to place for meetings and client home visits, so I can't be changing all the time). If it's especially hot, I take off my jacket and tie and roll up my sleeves, and obviously, I go slow. Sometimes I work a longer ride into my commute (~20 miles), and on those days I carry my dress shirt carefully folded in my bag, along with a clean undershirt and some deodorant, and ride in work pants and a biking shirt. If I plan a long ride, I leave some cool-off time at the end before having to be around other people.