I’m actually off duty this Sunday and will be worshiping with my parents in Winfield, Kansas.  Here is a call to worship we’ve used in the past for Trinity Sunday.  (I think it was two years ago now that my preaching instructions from the worship committee for that Sunday were to “just explain the Trinity to us–and keep it short.”)

Call to Worship

Loving God, Life of the universe,
we gather to worship You.
Great Creator who created us in Your image
we gather to worship You.
Holy Redeemer who became flesh and lived among us;
we gather to worship You.
Sustaining Spirit who breathes into us always the holy breath of Life,
we gather together to worship.