St. John Chrysostom, whom we remember today, was one of the great theologians and bishops, and perhaps the greatest preacher in the early centuries of Greek Christianity. Born in Antioch in 349, he spent some years as a monk and apparently practiced extreme ascetism. Ordained a deacon in 381 and a presbyter in 386, his preaching brought widespread fame. Because of his renown, he was made Archbishop of Constantinople in 398. In Constantinople he repeatedly aroused the wrath of the imperial court and was banished twice and died in exile in 407.
He is most famous for his sermons, of which many survive. He attacked the ostentatious show of wealth and repeatedly urged his listeners to care for the poor. Here is an excerpt from a homily on Matthew 14:
For what is the profit, when His table indeed is full of golden cups, but He perishes with hunger? First fill Him, being an hungered, and then abundantly deck out His table also. Dost thou make Him a cup of gold, while thou givest Him not a cup of cold water? And what is the profit? Dost thou furnish His table with cloths bespangled with gold, while to Himself thou affordest not even the necessary covering? And what good comes of it? For tell me, should you see one at a loss for necessary food, and omit appeasing his hunger, while you first overlaid his table with silver; would he indeed thank thee, and not rather be indignant? What, again, if seeing one wrapped in rags, and stiff with cold, thou shouldest neglect giving him a garment, and build golden columns, saying, “thou wert doing it to his honor,” would he not say that thou wert mocking, and account it an insult, and that the most extreme?
Let this then be thy thought with regard to Christ also, when He is going about a wanderer, and a stranger, needing a roof to cover Him; and thou, neglecting to receive Him, deckest out a pavement, and walls, and capitals of columns, and hangest up silver chains by means of lamps. Homilies on the Gospel of Matthew, 50, (from http://www.ccel.org)
He is also famous for a series of sermons directed against Jews, the full texts of which can be found here.
In addition to his sermons and many other writings, The Liturgy of St. John Chrysostom continues to be used by Orthodox Churches. An English translation is found here.
The “Prayer of St. Chrysostom,” which appears in The Book of Common Prayer, is a late-medieval addition to the Liturgy of St. John Chrysostom and was not written by him.