BANA (Braille Authority of North America) has just released the new Braille Formats: Principles of Print-to-Braille Transcription, 2011. This completely revised publication is available in three accessible electronic versions: enhanced PDF, BRF, and online HTML. These are available at www.brailleauthority.org and are offered without charge.
This is an extensive revision of the previous formats publication. Appendix A of the new publication provides a quick reference of changes and additions.