Today's Saint (February 14): Valentine
According to pious tradition, Valentine was either a priest at Rome who was martyred under the Emperor Claudius (c. 269), or a Bishop of Terni, taken to Rome and also martyred, and whose remains were subsequently taken back to Terni. Not much else is known about either person, although they may even be the same person, in truth.
In any event, the association of Valentine with courtship and love most likely arose from the pagan festival of Lupercalia (mid February) at Rome, and therefore has nothing to do really with the saint in particular.
However, the day most assuredly reminds us that martyrdom may be a part of the calling of Christ, who reminds us all that "Greater love hath no man than this, that a man lay down his life for his friends." (John 15:13)
Books Worth Considering
The Concise Oxford Dictionary of the Christian Church
The Oxford Dictionary of Saints (Oxford Paperback Reference)
The Penguin Dictionary of Saints: Third Edition (Dictionary, Penguin)