Here are some tricky things to be aware of, and to mention to patrons when you are helping them:
IPUMS International Research Data Enclave available to researchers who need access to confidential information. Researchers must go to the University of Minnesota to access.
Fertility, Mortality, and Migration records are also available for select countries and years. These don't fit into the usual data structure so you have to download those seperately.
IPUMS-Intl also offers geographic variables for mapping in a GIS.