The Church of Jesus Christ of Latter-Day Saints (LDS) are often referred to as the Mormons. Their theology places an emphasis on tracing family history and they have microfilmed millions of records worldwide that are of use in genealogical research. The records themselves are not necessarily Mormon-related, but are useful in tracing family history of any person. The LDS make these records available at their Family History Centres for a small hiring fee to any person.
The LDS Family Search website has countless records from the IGI and other sources, all free to view.