Marathonguide dot com

Pretty good site for useful articles on Marathon related topics (it does what it says on the tin). Particular articles that caught my attention were: -

Heart Monitor Training

Heart monitors are devices that are designed for wear during strenuous exercise, and serve the purpose of measuring and recording your heart rate, while giving you instant feedback about the work level of your heart. The fitness of the heart is the key to one's aerobic endurance - sometimes called 'cardiovascular respiratory endurance'. Both for health and racing reasons, aerobic endurance is a point of focus for almost any runner. Heart monitors are one of the most effective aids for tracking and developing your progress on the path to increased aerobic endurance.

Fuel on Fat For the Long Run

Always nice to know that fat is necessary for runners!

Developing your fat engine will increase the amount of energy you can generate, reduce the amount of carbohydrates you use, and stretch out the glycogen supply during long runs. Added together, you have a more stable and enduring energy supply, better endurance, and faster finish times.

Running and Fitness Calculators

Very useful for working out pacing, nutrition, heart rate etc