The following is a daily prayer I developed based on Doreen Valiente's Charge of the Goddess. It could rightly be used for just about any Goddess in the pantheon, but personally I most often use it as devotion to Demeter or Hera.
Beloved Mother, Source of All Living, Light and Life of Worlds Without end, yours is the ecstasy of the Spirit. Yours is joy unto all. Yours is the everlasting law of love. Teach us this day to live your law--to keep pure our highest ideals, that nothing or no one may turn us aside from our Divine Inheritance, from communion with you. Bless us with an awakening of our souls that they may heed your call and arise unto you--that we may know ourselves as you know us, in truth, and love ourselves and our fellows all the more because our hearts and vision have been so filled. Grant us this day of your balance, your beauty and strength, wisdom and abundance, power and compassion, honor and humility, mirth and reverence. As we seek for you, let us also seek within ourselves, and let us ever remember the greatest of all truths; that as our lives flow from within you, so you live and flow within us.