In addition to the Tompkins County NY Genweb site, I also recommend the Tompkins County Library’s website . The site has an obituary index from the Ithaca Journal, beginning in 1860 through 1999. Not all years are available, but the ones that are, are broken down by alphabet for easier searching. The Index to Trumansburg Newspapers is also available here.
This site features a number of interesting items. A volunteer named Olympia is developing an index of births and deaths – Olympia’s Index features deaths from December 1854 through June 1874, and then 1914-1920, and births January 1915 – April 1918. These indexes are arranged by name and also by date.
There are some biographies, rural directories, narratives and memoirs, local organizations, and yes, you can even read about my great-great-great-grandmother in The Pioneer Clevelands.
This site has a bunch of fun stuff for those researching in Tompkins County.