Clark County, OH Genweb Project a collection of online resources for genealogy researchers
Census-Online.com - census transcriptions for  Clark Co.
Clark County, OH Genealogy Forum read and post messages about your ancestors for this county
Clark County 1818 Tax Lists
Revolutionary War Vets in Clark County
WWI Draft Registrations  men living in the county ages 18-45 in 1917/18
The Tombstone Transcription Project - cemeteries for Clark Co. OH
US GenWeb Archives for Clark County cemeteries, newspapers, wills, military rosters etc recorded online
1830 Census Index

Additional Resources

Ohio Newspaper Search enter your ancestor's name to instantly search the world's largest newspaper archive; over 12 million newspaper pages
Ohio Birth Records
Ohio Marriage Records
Ohio Divorce Records
Ohio Death Records