Here are some sites which I have found useful in my research ....

A list of occupations
Access to Archives
Archaic medical terms
Australian War Memorial
Births Deaths and Marriages Exchange
Commonwealth War Graves Commission database
Cornwall 1871 Census
Cyndi's List of Genealogy Sites on the Internet
Deciphering old handwriting
Digital Library of Historical Directories
East Surrey FHS
Family Relatives
Findmypast (formerly 1837online)
Free BMD project
Genealogy Gateway To The WebTM
LDS Family Search Site
Leitrim-Roscommon home page
NSW registry of BDM
Origins Network
PRO 1901 census
PRO DocumentsOnline (wills)
S & N genealogy supplies (censuses)
Stepping Stones
The Sole Society
US 1880 census