SSDI (Social Security Death Index) links and U.S. Railroad Retirement Board

Searching the Social Security Death Index in One Step
http://www.stevemorse.org/ssdi/ssdi.html

Searching SSDI tips and pointers
Obituary Central - An obituary database and headquarters for finding obituaries
http://www.obitcentral.com/obitsearch/ssdi.htm

Social Security Death Index (SSDI) - FamilySearch (free to search - from FamilySearch.org) has over 80 million entries - updated to February 2009
http://www.genesearch.com/socialsecurity.html

Social Security Death Index Search @ Family Tree Legends (Free)
http://www.familytreelegends.com/records/ssdi

SSDI @rootweb.com
http://ssdi.rootsweb.ancestry.com/cgi-bin/ssdi.cgi?cj=1&o_xid=0...

Social Security Death Index (free to search from Genealogy Bank)
has over 84 million records - updated to early July 2009 (updated weekly)
http://www.genealogybank.com/gbnk/ssdi/?kbid=9064&m=9

U.S. Railroad Retirement Board ~ Genealogy Research
http://www.rrb.gov/mep/genealogy.asp