There are a few "encyclopedia" type articles which introduce the reader to the concept of the Sociology of Religion. The Sociology of Religion, which has a Durkheimian emphasis.
Sociology of Religion Wiki essay
Max Weber Wiki essay
Emile Durkheim Wiki essay
New World Encyclopedia Covers churches sects, cults,denominations and comtemporary sociology of religion
Hartford Institute for Religion Research - I like this resource the best. It covers online articles, bibliographies and syllabi, sociologists of religion, associations and research resources. In the latter, I found research methodology sites.
YAHOO'S Sociology of Religion - There are a couple of sites that you will find interesting, especially those with full texts on the Sociology of Religion (auf Deutsch) and some related to Max Weber.
Religious Movements Page (from the University of Virginia) - This is an outstanding source for encyclopedic scope of different religions. The essays are long and contain links to other subjects.
H- AmRel - This is a discussion site.
Center on Religion and Democracy - Students will find the library useful as it has links to such source material as the Salem witch trials, legal documents and other reference works.
Anthropology of Religion - Covers various religions.
American Religion Data Archive - provides data on churches, church membership and religious groups.
Adherents.com - This site would answer "How many Methodists live in Indiana?" or " What percentage of Jews are Reformed?"Church Growth Modeling - This site does have some resources encountered elsewhere on this page but the modeling and statistical information are off to the left.