Maybe you already know the incomparable help from the Stephen P. Morse web sites for searching for ship passengers and immigrants. He has a site for helping search the soon-to-be released 1940 USA census. Included on his site is a tutorial for searching the online 1940. This is critical, as the 1940 is not indexed by name or address. It will be necessary to know the Enumeration District. As far as I can tell, his sites are not commercial. I provide both the “front” page for searching the 1940 (available as of April 2, 2012) AND a most helpful tutorial for searching the 1940.

“front” page:
http:/
/stevemorse.org/ed/ed.php

tutorial:
https://
stevemorse.org/census/quiz.php