What virtue means in the context of Taoist practice might be a bit different from what our minds normally conjure, when we hear the word "virtue." De (Te) has less to do with adhering to externally-mandated (religious or secular) codes of conduct, and more with allowing our actions to emerge from the spontaneous perfection of the Tao. Being virtuous, for a Taoist practitioner, is connected closely with the practice of wuwei: the mysterious "action of non-action."
What this means, so far as I can tell, is that our egoic will is surrendered to, or merged with, the "will of Heaven," i.e. the rhythms of the natural world, as they emerge from the Tao. Having thus surrendered, we gain access to an infinite Intelligence, which knows, spontaneously, what the "right" action is, in each and every moment. Learning to abide in this state of wuwei is obviously a process - whose perfection comes only in moments when we are manifesting our True Nature as Immortals.
The Virtues of the Organs
At the level of our human body, the notion of virtue is a bit different. According to the Five Element System, each of the major yin organs has what is known as its "virtue." This refers to an emotional state that expresses when the energy of the organ is balanced and free-flowing. So, for instance, the virtue of the Liver is kindness, and the virtues of the Kidney are wisdom and a child-like wonder.