June 15 is the Great Feast of Pentecost. "Lo, we celebrate the Feast of Pentecost, the presence of the Spirit, the fulfillment of the promise and the completion of the hope. How wonderful is this mystery. ... Thou hast renewed for thy Disciples, O Christ, a different kind of tongues, that they might therewith proclaim that thou art the immortal Word and God who granteth our souls the Great Mercy. The Holy Spirit provideth all; overfloweth with prophecy; fulfilleth the Priesthood; and hath taught wisdom to the illiterate. He hath revealed the fishermen as theologians. He bringeth together all the laws of the Church." (The Pentecostarion)
Click here to listen to Fr. Patrick Reardon's homily on Pentecost at Ancient Faith Radio.  Children will enjoy listening to Archdiocese Featured Author Chrissi Hart  read from a Conciliar children's book about the Feast . The audio can be found here.  Finally, here's a good introduction to Pentecost prepared by the Greek Orthodox Archdiocese.