Philip Jenkins
Distinguished Professor of History and Religious Studies
NUREL is a good starting place.
This is a major resource collection from the University of Virginia.
Particularly on international and European movements, one of the best resources is CESNUR, the Center for the Study of New Religions.
A massive bibliography by Rob Nanninga.
Sites that provide an excellent launching point for studying NRMs include this one from the Hartford Institute, and one from academicinfo.net.
Christian apologetics and anti-cult materials
Pagan and indigenous religions.