I ran across this above image this morning on Facebook, and was inspired to do a post on chanting.
Hare Krishna Hare Krishna
Krishna Krishna Hare Hare
Hare Rama Hare Rama
Rama Rama Hare Hare
“Chant Hare Kṛṣṇa and be happy. Thank you. Hare Kṛṣṇa.” (Srila Prabhupada Lecture & Initiation Seattle, October 20, 1968)
“…chant dance, take prasadam and be happy.” (Srila Prabhupada Letter to Saksi Gopala 6 December, 1975)
“Following in the footsteps of Lord Caitanya Mahāprabhu, the Kṛṣṇa consciousness movement is distributing the Hare Kṛṣṇa mahā-mantra and inducing people all over the world to chant. We are giving people an immense treasury of transcendental literature, translated into all the important languages of the world, and by the grace of Lord Śrī Caitanya Mahāprabhu this literature is selling profusely, and people are chanting the Hare Kṛṣṇa mahā-mantra with great delight. This is the preaching process of the Caitanya cult. Since the Lord wanted this cult preached all over the world, the International Society for Krishna Consciousness is acting in a humble way so that the vision of Śrī Caitanya Mahāprabhu may be fulfilled all over the world, especially in the Western countries.” (purport to Sri Caitanya-caritamrta 1975 Adi-lila 16.19)
Also:
Vedic sanskrit references for chanting the Hare Krishna Maha Mantra More
The Hare Krishna Movement 