Hymen piercings are extraordinarily rare piercings. The hymen is the mucous membrane partially closing the vaginal opening. "Virginity" is generally considered lost when the vagina is penetrated, ripping the hymen. Two photos of hymen piercings have appeared on BME/extreme (one in Brazil, one in Germany), but there are currently no experiences to go with them. Healing times/factors are unknown, as is the practicality of this unusual modification.
As of 2008, Hymenoplasty has been performed 2-4 times a week at some clinics for roughly $3000 for giving the illusion of virginity. Whether or not a woman would willing undergo hymenoplasty so that she may pierce her neohymen remains to be seen.