There are a number of sources to help us find clergy/church leaders. Most are not published in large numbers, or have wide distribution so one has to be a bit of a detective to track some of these down.
There are a few cities that have books published on all the ministers of that city, Pittsburgh, PA is one of these. While these comprehensive books are great, they are few and far between.
A wider distributed type of book would directories of ministers of a certain faith, such as Who's Who in Methodism, Who's Who in the Methodist Church, or Who's Who in World Jewry. While they don't have every name in the faith, they do have a large amount of data.
On the local level there are a number of sources, County Histories, Centennial Histories, and local Church Histories. They are not usually found outside of the locale in which they were written about, though they often enjoy wide distribution within the community. They often give the most detailed biographies of the church leaders and families.
Another source, which are usually hard to find, are the annual reports of the different conventions, synods, encampments (or what other term they may apply). These often have lists of all the ministers of that diocese/synod/organization and which communities they serve. Finding these can be tricky. Local libraries and historical societies may not be able to devote shelf space to a resource with limited appeal.
Worldcat.org is your friend as Inter-Library Loan may be your only option to view some of these sources. Most of these won't be found online because of copyright issues, limited demand or a very small distribution.
What other sources have you discovered for finding the Leaders of the Faith?