The Patient Protection & Affordable Care Act
Affordable Care Act Timeline (web site) – explains which provisions of the ACA have already been enacted and when you can expect the rest to change.

Reference Bookshelf
AAFP Guide to the ACA (web site) – This helpful web site run by the AAFP provides resources to help educate you and your patients on changes to the health care system instituted by the ACA
HealthCare.Gov  (web site) – A web site maintained by the U.S. Department of Health & Human Services with easy-to-find information about changes in health policy and how legislation will affect your health and your practice