Census-Online.com - census transcriptions for Union Co.
Union County GenWeb Projectcollection of online resources for genealogy researchers
Union County Message Board read and post messages with other genealogy researchers of this county
Union County, PA - at the American Local History Network Site useful links to genealogy records
Union County, PA Genealogy Forum read and post messages about your ancestors for this county
Union County Surnames
The Tombstone Transcription Project - cemeteries for Union Co; PA
US GenWeb Archives for Union County cemeteries, newspapers, wills, military rosters etc recorded online here

Additional Resources

Pennsylvania Obituary Search enter your ancestor's name to search the world's largest newspaper obituary archive; over 3 Billion newspaper articles
Pennsylvania Birth Records
Pennsylvania Marriage Records
Pennsylvania Divorce Records
Pennsylvania Death Records