One of the databases available for northern Kentucky is hosted by the Kenton County Public Library. This site is located at http://apu.kenton.lib.ky.us/gen/gendb.php. Many of the records focus on Kenton County and the area around Covington, Kentucky and include cemetery, church, Civil War, census, birth and death records. If your families ever lived in this area of Kentucky this is a great resource.
A good source for death (1911-1992), marriage (1973-1993) and divorce (1973-1993) records is the Kentucky Vital Records Index located at http://ukcc.uky.edu/vitalrec/. Another death index database can be found on the Rootsweb website at http://vitals.rootsweb.ancestry.com/ky/death/search.cgi. This database includes an index of almost 3 million names between 1911-2000. If you want to see the actual death certificates you can find them at http://kyvitals.com/.
The Kentucky Land Office has a variety of land grant databases on their web page at http://sos.ky.gov/land/search/. This site includes some really great databases including digital copies of the Revolutionary War Warrants prior to 1792, West of Tennesee River Military Patents, Virginia and Kentucky Patents, and several others. These land grant databases include copies of the grants, surveys and other documents supporting land claims.
The Kentucky Cemetery Catalog can be found at http://126.96.36.199/cemetery.asp. This database includes hundreds of thousands of names from cemeteries across Kentucky. All of the information was gathered by volunteers.
The Kentuckiana Digital Library has links to several collections at http://kdl.kyvl.org/. These collections include newspapers, books, images, maps, oral histories, manuscripts and journals. The newspaper archives is a little cumbersome to navigate but once you get through the links you can see the actual pages of the paper with your search term highlighted.
Well, I hope these databases help in your search for relatives from Kentucky.