Over the centuries devotion to St. Agnes has been manifested in many ways. Some of these include:
A few days after Agnes’ death, her foster-sister Emerentiana, was found praying by her tomb. When she refused to leave and reprimanded the pagans for killing her sister, she was stoned to death. Emerentiana was also later canonized.
In the 4th Century, Constantia, the daughter of Constantine, built a basilica on the site of St. Agnes’ tomb after being cured of leprosy while praying there. St. Agnes’ bones remain there preserved under the altar in Rome’s Piazza Navona, but her skull is preserved in a separate chapel. Saint Agnes’ basilica was entirely remodeled by Pope Honorius (625-638) and remains largely unchanged today, almost fifteen hundred years later.
St. Agnes is one of seven women, who along with the Blessed Virgin, are commemorated by name in the Canon of the Mass. 
It is customary on Saint Agnes’ feast day for two lambs to be brought from the Trappist abbey of Tre Fontane in Rome to be blessed by the Pope. On Holy Thursday they are shorn, and from the wool is woven the pallium which the pope gives to a newly consecrated metropolitan archbishop as a sign of his jurisdiction and his union with the pope. 
The Congregation of Sisters of St. Agnes is a Roman Catholic religious community founded in 1858 and based in Fond du Lac, Wisconsin. The Sisters of St. Agnes … are called to respond particularly to those whose faith life or human dignity is threatened. 
St. Ambrose told St. Agnes’ story and others in “De virginitate” and had this to say about her: “Behold therefore in the same victim a double martyrdom, one of modesty, the other of religion. She remained a virgin, and obtained the crown of martyrdom.” 
Hymns, poems, and plays have been written about St. Agnes. The Roman poet Prudentius composed a hymn in honor of St. Agnes in the 9th century, “Agnes Beatae Virginis.” Tenth-century nun and poetess, Hrotsvitha, wrote a play about St. Agnes and Grace Andreacchi wrote a play based on the legends surrounding Agnes’s martyrdom.
During medieval times, the memory of St. Agnes inspired rituals for unmarried chaste couples. A young woman would forgo supper on the eve of St. Agnes’ feast day in order to dream about her future husband. Other customs involved sewing one’s stockings together, or putting rosemary in one’s shoes, also to glean a vision of one’s future mate. In parts of Scotland grain was scattered in cornfields by unwed men and women who recited a poem as they did so asking for guidance to “let me see/The lad (or lass) who is to marry me.” Nineteenth-century Romantic poet John Keats wrote an epic poem, “The Eve of St. Agnes,” linked to these superstitions.
St Agnes is venerated as a saint in the Roman Catholic Church, Eastern Orthodox Church, the Anglican Communion, and Lutheranism. 
There are literally hundreds of churches and schools named for Saint Agnes throughout the world. Here are just a few of our U.S. neighbors:
– Saint Agnes / Holy Trinity Catholic Church, West Mifflin, PA
– Saint Agnes Catholic Church (1873-1993), 5th & Robinson Sts, Oakland, Pittsburgh, PA
– Saint Agnes Catholic Church, West Chester, PA
– Saint Agnes Catholic Church, Arlington, VA
– Saint Agnes Catholic Church, Nashville, IN
– Saint Agnes Catholic Church, Phoenix, AZ