Cook County; Resthaven Cemetery
Cook County Coroner's Inquest Record Database 1872-1911
Cook County;  Palatine Township, Salem Cemetery
Cook County, 1850 Mortality Schedule
Cook County, IL Genweb Project a collection of online resources for genealogy researchers
Census-Online.com - census transcriptions for Cook Co.
Cook Co. Surnames
Cook County Coroner's Inquest Record Index, 1872-1911 74,160 records in the database
Illinois Public Domain Land Tract Sales Database - for Cook County select this county and then enter the surname (at least first 2 letters) of the person whom you wish to search on  (a government database of over 550,000 19thC land sales in Illinois - info on obtaining original copies is here )
Genealogy Trails History and Genealogy Project - Pages for This County you will find user contributed records of births, deaths, marriages, military and newspaper extracts at this site
Interment.net - cemeteries for Cook County
The Tombstone Transcription Project - cemeteries for Cook Co. IL
US GenWeb Archives for Cook County cemeteries, newspapers, wills, military rosters etc recorded online

Additional Resources

Illinois Obituaries enter your Illinois ancestor's name to search obituaries in over 75 million newspaper pages
Illinois Birth Records
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Illinois Divorce Records
Illinois Death Records