Here are some links to research on congregations:
The State of the Church in America: Hint: It’s not Dying by Ed Stetzer – a helpful interpretation of the research data
US Congregations data – http://www.uscongregations.org/
Faith Communities today – Faith Communities Today website and their Facts of Growth report on the change in congregations between 2000-2010.
The Association of Religion Data Archives – http://www.thearda.com/rcms2010/
ELCA by the numbers (June 2012) – Numbers Tell a Tale of Change – Some up, done – always onward by Daniel Lehmann. The Lutheran, June 2012, access at http://www.thelutheran.org/article/article.cfm?article_id=10713
American Religious Identification Survey 2008 (Click the image below for a link.) http://commons.trincoll.edu/aris/publications/2008-2/aris-2008-summary-report/