General resources

Resources useful for researching a family tree.

Genforum
http://genforum.genealogy.com/
(individual surname, state and country message boards)

Rootsweb
http://www.rootsweb.ancestry.com/
(message boards, etc.)

ISTG (Immigrant Ship Transcriber's Guild)
http://www.immigrantships.net/index2.html
(passenger lists)

Castle Garden (New York port used before Ellis Island)
http://www.castlegarden.org/

Family Search (the Mormon Church's new database)
http://pilot.familysearch.org/recordsearch/start.html#

Migrations.org
http://www.migrations.org/index.html
(surnames by state and county)

Ellis Island
http://www.ellisisland.org/
(New York port immigrants came into from 1892-1924)

SSDI (Social Security Death Index)
http://ssdi.rootsweb.ancestry.com/

Genealogy Trails
http://genealogytrails.com/

Cyndi's List
http://www.cyndislist.com/
(I've never found anything useful on it but some people swear by it)

Ancestry.com
Has sources you can't get elsewhere but you have to pay for it.
The Sidney library has it for free on one of their computers.

County courthouses, local libraries and churches.

State vital records. Every state has a website where you can find out
how to access records.