Resources

Books

Open Mind Open Heart by Thomas Keating.
This is the standard introductory text to Centering Prayer.

Invitation to Love by Thomas Keating

If you are coming to Centering Prayer without a background in a Christian community, you may like these books by Cynthia Bourgeault:
Centering Prayer and Inner Awakening and The Heart of Centering Prayer.

The Path of Centering Prayer, Deepening Your Experience of God by David Frenette is a good book to refresh your practice.

Online Materials

A wealth of video recordings and articles is available from the resources page of Contemplative Outreach (U.S). In particular there is an in depth online course, Spiritual Journey freely available. If you do two lessons a week, you'll complete the course in a year.

YouTube has many recordings of Thomas Keating, Cynthia Bourgeault, David Frenette, Carl Arico, Mary Dwyer.