Shiva Ratri

Shiva Ratri is a festival in honor of Lord Shiva and is one of the three sacred nights of the Tantric tradition. In Shiva Ratri one observes vows such as upavasa or “rigorous fast of atonement” jagarana or “to pass the night without sleeping” and sat katha sravanam or “to listen to holy scriptures.” During Shiva Ratri Lord Shiva is worshiped by singing hymns, chanting the Rudram, repeating the sacred mantra "Oṁ Nama Shivaya" and bathing the Shivalingam with milk, yogurt, ghee, sugar, and honey. 

Om Shivaya, Om Shivaya,

Shambho Shankara, Om Shivaya

http://www.thebuddhagarden.com/mahashivaratri.htm