From: http://www.coolrunning.com/major/97/training/swit0214.htm#run

Becoming a One Hour Runner The key component of this program is the one long run per week. It builds up endurance and lays the foundation for further progress. Weeks 1 - 3: Right now you are running 30 minutes a day, 3 days a week. Your weekly commitment of time is 90 minutes. Continue doing this for three weeks. Week 4: Run 30 minutes, 29 minutes, 35 minutes. Weekly total: 94 minutes Week 5: Run 30 minutes, 32 minutes, 38 minutes Weekly total: 100 minutes Week 6: Run 30 minutes, 33 minutes, 41 minutes Weekly total: 104 minutes Week 7: Run 30 minutes, 34 minutes, 45 minutes Weekly total: 109 minutes Week 8: Run 30 minutes, 36 minutes , 49 minute Weekly total: 115 minutes Week 9: Run 30 minutes, 38 minutes, 54 minutes Weekly total: 122 minutes Week 10: Run 30 minutes, 40 minutes, 60 minutes Weekly total: 130 minutes A personal note: When you are trying to increase your distance, some days feel good and others feel awful. Listen to your body. Be willing to back off. There is no hurry. These schedules are designed for the best possible circumstances, and sometimes you just need more time to adapt. Never move on to the next higher distance until you feel totally comfortable with the one you did today. I can remember once doing the same mileage for three weeks before I felt I had the strength to add a bit more. I have many more tips and personal stories to help you be a better runner, to safely enjoy the sport, to eat properly and to help you select the right kind of shoes, clothing and sport bras. I encourage you to buy my book. by Kathrine Switzer - Program Director - Avon Running

Note: the book she refers to is: Running and Walking for Women Over 40, The Road to Sanity and Vanity (St. Martin's Press), By Kathrine Switzer