Samantabhadra is one of the great bodhisattvas in Buddhism. He is reknowned for his practices of generosity. In the Avatamsaka Sutra (“The Flower Ornament Scripture”, translated by Thomas Cleary), he is known as “Universally Good”. Chapter 3, The Meditation of the Enlightening Being Universally Good introduces Universally Good. Other chapters in this long and fascinating sutra present his teachings.
The Vows of Bodhisattva Samantabhadra Sutra is available on buddha.net. It contains background information about the bodhisattva and related prayers.
In the Gelukpa school of Tibetan Buddhism, a common dedication prayer is “The Extraordinary Aspiration of the Practice of Samantabhadra” (Samantabhadracarya pranidhana in Sanskrit). In the FPMT prayer book volume 1, it is referred to as the King of Prayers. Lama Zopa Rinpoche suggests that we also read this prayer on behalf of someone who has died.
Finally, the book Garland of Jewels: The Eight Great Bodhisattvas by Jamgon Mipham contains stories about several main Bodhisattvas including Samantabhadra.