The internet contains a wealth of resources to facilitate genealogical research. Here are some of the more popular links.

Ancestry.com
Christine’s Genealogy Website (African-American Genealogy)
Cleveland Public Library Necrology (Obituary file)(Obituary file 1850 1975)
Cyndi’s List (Over 330,000 Genealogical Links!)
Daughters of the American Revolution
Death Indexes and Records Online
Digital Shoebox Project
Family Search-Church of Latter Day Saints
Findagrave.com-Jefferson County Ohio Cemeteries
Genealogy Online
Heraldry on the Internet (Coats of Arms)
Jefferson County Cemeteries
Jefferson County (Ohio) Genealogical Society
Jefferson County GenWeb 
National Archives and Records Administration
Ohio Byways
Ohio Death Certificate Index
Ohio Genealogical Society
Ohio Historical Society
R B Hayes Obituary Index
USGenWeb Project