FamilySearch Labs
FamilySearch is a website produced by The Church of Jesus Christ of Later Day Saints, containing a lot of genealogical records. FamilySearch Labs is a project still in beta stage, but provides access to a database of census, military and vital records.
Random Acts of Genealogical Kindness
An index by state and county of volunteers willing to look up obituaries and local records, as well as take photographs of tombstones, only charging for copying fees and in some cases mileage. For vital record lookup, don't forget to check the county where the state capitol resides, because there are often statewide records there. Sometimes local counties might be more restrictive on access to records than the state archives are, even though the records are identical.
RootsWeb
Social Security Death Index, Surname message boards and mailing lists.
National Archives Archival Databases
The National Archives has Enlistment records for military personnel, lists of prisoners of war, passenger lists, and other information.
Online Directory Site
An index of available City, County, and Rural Directories. Operated by Miriam Midkiff of the Ancestories genealogy blog, the website was created in May of 2009, and is a work in progress. The ultimate goal of the website is to be complete for US and Canada.
Subscription Sites
Ancestry
A large collection of databases including the US Census indexed through 1930; Birth, Marriage and Death Records; Military Records; Immigration Records.
Footnote
Databases include, but are not limited to, Civil War, WWII, and Naturalizations