We find the LDS Church's
http://www.familysearch.org/ to be invaluable.
In addition to browsing the IGI, Ancestral File, and 1880 U.S. Census,
use it to access the Family History Library Catalog
and prepare for your next research trip to Salt Lake City
or your local Family History Center!
Keep up with genealogy and technology at
http://www.gentech.org/, including the GENTECH Genealogical Data Model.