I like the rich theology of the appointed Collect and Proper Preface for the Feast of Pentecost found in the Book of Common Prayer. However, I felt inspired to offer up a slight variation to be used in either one of those places. As with any Preface/Collect I compose, you could also use this prayer—should you so desire—as an opening preface or closing collect for the Prayers of the People.
Come Holy Spirit!
We praise you O God, who on this day did sent your Holy Spirit upon the disciples at Pentecost giving birth to the church. You opened up the gates of eternal life to all people: slave and free, male and female, young and old, Jew and Gentile. Empower us to share your Gospel to peoples of all nations, tribes, and tongues. Grant that we may be anointed afresh by your Spirit, equipped for your ministry, led into all truth, and consecrated for service in your Kingdom, and all for your glory.