Mantra Calligraphy
Gayatri Mantra - composed by the Vedic sage Vishvamitra spontaneously upon emerging from Nivikalpa Samadhi (greatest spiritual trance). The preamble (Om Bhur Bhuva Svaha) is from the Yajur Veda. It is a preamble for many mantras. The actual Savitri (Solar) Gayatri mantra (Tat Savitur...) is a three line mantra (-tri means three) from the Rigveda (3.62.10). This is the most famous and revered mantra of India, and the daily practice of millions of contemporary Hindus. Considerable power on all levels is attributed to the Gayatri.

Om Bhur Bhuva Swaha
(Om Bhoor Bhoova Swa-Ha)

Tat Savitur Varenyam

(Tat Sa-Vidoor Va-rain-yam)

Bhargo Devasya Deemahi

(Bhaargo They-Vas-Ya Dee-Mahi)

Deeyo Yo Naha, Prachodayaat

(Thee-Yo Yo-Na-Ha, Pra-Cho-Da-Yaat)

Om Bhur Bhuva Swaha
(a preamble to the main mantra)
We invoke the earthly, physical spirit,
the world of our mind,
and the world of our soul.

Tat Savitur Varenyam
Tat : THAT, the Supreme Being
Savitur : the radiating source of life
Varenyam : most adorable, most desirable

Bhargo Devasya Deemahi
Bhargo : luster and splendor
Devasya : Divine or Supreme
Deemahi : We meditate upon

Deeyo Yo Naha, Prachodayaat
Deeyo : spiritual perception
Yo : He Who, and
Naha : Our. Finally,
Prachodayaat, : May he Inspire, Guide, Illumine.

A summary translation ( you will find many various on the web)
"We invoke That Supreme Essence
which manifests as the earthly spirit, the world of our mind, and the world of our soul.
Oh, Supreme Being, most adorable radiating source of life,
We meditate on Thy Divine Splendor. May thou illumine our spiritual perception."

A good instructional on some pronunciation in the Gayatri:

To see how the written Devanagari reflects the spoken mantra:

“Of the many methods of yoga, one of the most potent is the yoga of Gayatri mantra. Mantras have powers to endow one with remarkable abilities. The Gayatri mantra gives the devotees spiritual as well as material benefits.”
     — Ramana Maharshi

“I tell people that due to the sadhana of Gayatri hard austeries have been rendered unnecessary. The treatest of siddhis can be obtained by the japa of Gayatri. The Gayatri mantra is small but its powers immeasurable. “
    — Ramakrishna Paramahamsa

"Gayatri is a mantra of righteous wisdom and therefore, it has been called a be-jeweled crown of all the mantras."
    --- Swami Vivekananda

"Gayatri mantra chanted with a calm and steadfast mind helps one overcome even those obstacles which otherwise appear insurmountable."
   --- Mahatma Gandhi

"Of all the Mantras, the Supreme and the most potent power of powers is the great, glorious Gayatri Mantra. It is the support of every seeker after Truth who believes in its efficacy, power and glory, be he of any caste, creed, clime or sect. It is only one's faith and purity of heart that really count. Indeed, Gayatri is an impregnable spiritual armor, a veritable fortress that guards and protects its votary, that transforms him into the Divine ."
   --- Swami Sivananda

"Infinite energy rests in the Gayatri mantra."  
   --- Sri Aurobindo

Fix Mind on the Ultimate Cause of the Universe
For what else is there to worship?
It is streaming light of knowledge
Washing out our imperfections.
What perfection!

- India Riaz