Stuck at a Weight Loss Plateau

Let's say you've been losing a pound or two a week, and are well over half-way to reaching your weight loss goal. Then comes a few weeks when nothing happens and the scale doesn't move. What do you do to get it going again? What works for you? A new exercise activity? Exchanging some food items for new ones? Increasing your intensity of workout? Let's hear from every one of you who have ever experienced plateauing - it happens to all of us at one time or another!