Phillip Moffitt discusses mindfulness and how the practice of mindfulness is related to the Buddha’s teaching on liberation from stress and suffering. You can find his article here: What is the Mindfulness of the Buddha?
Also on the Spirit Rock website, Sean Oakes gives an introduction to mindfulness that includes a brief introduction to the four foundations of mindfulness, the areas of our experience that the Buddha suggested were especially helpful for the practice of mindfulness. You can find his article at this page: The Four Foundations of Mindfulness.