If we're being virtuous, we clean up the kitchen during the down time. Five minutes of dish-washing while the sauce cooks a little longer means five less minutes of clean-up on the other end!
If we're feeling more lazy, we often end up reading - our next most favorite past time after cooking. We'll read the other articles in the magazine we're cooking from or flip through cookbooks. If we're in the middle of an especially good novel, we might even bring it into the kitchen to read a few paragraphs in between chopping and simmering!
What do you do while you wait between cooking tasks?