Pentecost is one of my favorite Christian holidays. This year it falls on May 11, the same day as Mother's Day. Pentecost was a Jewish holiday, and the followers of Jesus were gathered to celebrate it shortly after the resurrection of Jesus when little flames appeared above each of their heads, representing the Holy Spirit of God. We still celebrate this holiday every year. A fun way to celebrate is by creating a candle display, either on the communion table or some other spot near the front of the church.
You can also adapt the Tibetan idea of making prayer flags. Since the holiday is associated with the Holy Spirit, which blows through the people like a wind, it is a good way to involve people in celebrating Pentecost. Prayer flags are simple cloth squares on which people write their prayers. They are generally strung on long strings and hung where the wind will catch them. Tibetans leave their flags up and allow them to unravel in the weather, but you can take your flags down after the holiday if you like.