At least three different Saint Valentines, all of them martyrs, are mentioned in the early martyrologies under date of 14 February
Here is CatholicBrain's index of Saints. This is a great resource for learning about the lives of the saints at home or in the classroom!
Hermitess, Originally from Egypt, she was supposedly a relative of St. Victor the Theban Legion.
Saint Vergilius of Salzburg
Irish-born Abbot of St. Peter's monastery at Salzburg. He held that the earth was round, for which St. Boniface accused him of heresy. Vergilius freed himself of the charge, and went on to become a missionary, dying in 789
Benedictine virgin and recluse. Originally from a noble family of Castelfiorentino, Tuscany, Italy, she went on a pilgrimage to Santiago de Compostela and, after returning, had herself walled up in a hermitage near the Elba River.
Veronica is a name popularly given to one of the women who accompanied Christ to Calvary. 'Veronica' is an abbreviation of 'vera icon' (true image), and the woman now called Veronica is said to have offered a towel to Christ, on which he left the imprint of his face
Saint Veronica Giuliani
Capuchin, who died in 1727
Bishop of Oldenburg, who died in 1154
Saint Victor the Moor
Martyr executed at Nicomedia, with a group, including Zoticus,Antoninus, Theonas, Chrysophorus, Severian, Acyndius, Zeno, and Caesareus.
Bishop of Pettau, an ecclesiastical writer, martyred in the Diocletian persecution
Bishop of Trent, martyred 26 June, 405
Also called Maldegarius, married to St. Waldetrude. Their four children are also among the saints. SS. Vincent and Waldetrude both entered monastic life, he founding the monasteries of Hautmont and Soignies. He died in 677
Saint Vincent Ferrer
Spanish-born Dominican missionary, who died in 1419
Saint Vincent of Saragossa
Deacon, a native of Saragossa, martyred in 304
Bishop of Cambrai-Arras, born about 620
Monk, archbishop of Arles
Martyr in about 171. Husband of St. Valeria (also a martyr), and father of SS. Gervasius and Protasius
Saint Vitalis and Agricola
Vitalis was a slave, converted to Christianity by his master Agricola. Both were martyred at Bologna about 304
Saint Vitalis of Savigny
Founder of the monastery and Congregation of Savigny. Died 1122
Saint Vitus, Modestus, and Crescentia
According to the legend, martyrs under Diocletian