A few more helpful sites and tips:
http://www.familysearch.org/
(1880 census is searchable for free)
http://www.skpub.com/genie/index.html
(some older census images are available for free)
Also, in addition to tax records, check the marriage records and conveyance records, do a title search through the vendor-vendee index to trace the transfer of family property. It often passed from one relative to the next.
(Generally, these are all available at the clerk of court's office or perhaps even your local library.)
A number of you mentioned the social security death index at ancestry.com, but you may also try a search at the one provided (for free) via Rootsweb at the address below:
http://ssdi.genealogy.rootsweb.com/
Rootsweb has links to a variety of local resources, as does USGenWeb. Happy hunting!
