Full mudguards, with mudflaps. Rain jacket (or even better, a rain cape). Wool shirts (year 'round as they keep you warm in the winter, they don't stink, and they can go a week or so between washings). Studded tires in the winter months.
Granted, there are few people who can suddenly become full time bike commuters, unless you happen live in a flat area with a moderate climate. I've been bike commuting full time for about six years, and I did about half time for three years prior to that. I've gotten to the point that when I have to run an errand, I automatically think about hopping on the bike rather than in the car (and this includes errands that requires pulling the kids in the trailer).
Granted, there are few people who can suddenly become full time bike commuters, unless you happen live in a flat area with a moderate climate. I've been bike commuting full time for about six years, and I did about half time for three years prior to that. I've gotten to the point that when I have to run an errand, I automatically think about hopping on the bike rather than in the car (and this includes errands that requires pulling the kids in the trailer).