If you are like me and you keep all your home/work/life tasks in one place, you might want to consider ordering your tasks by the location you most efficiently can perform them in. Some tasks you can only do at one particular location (like I can only do laundry or dishes at home).
Some tasks, like business calls, can only be done during the day. other tasks are best done at night. some, like calling, are most efficiently done while you are driving (because you cannot do much else in the car). before driving on trips more than 30 minutes, you can have a call list of the people you want to call. sometimes, if it is a new contact, you can even pre-type the numbers in my cell phone so you don't have to fumble while in the car.
My personal secret is to have a list of tasks do to when I am on the phone. these are generally low-CPU tasks (like cleaning up my house, reordering my contacts, typing up a business card, and other mindless tasks). Whenever I get a call I immediately switch to my phone task list and start crossing off to-dos while jabbing away.