Co. Derry Civil Parishes Map
Co. Derry Roman Catholic Parishes Map
Co. Derry GENUKI
Co. Derry IGP
Derry Genealogy (RootsIreland)
Derry County Archives at PRONI
Special Ingredients - Record Finding Aids
Co. Derry Church of Ireland Parish Records Finder
Co. & City of Derry Registry of Deeds Townland Indexes Timelines
One obvious thing to look out for when searching for any county-related resources is the interchangeability of the name. "Londonderry" dates from 1613 when the London guilds became involved in the Plantation of Ulster and when the original county name of Coleraine was replaced too. Both names are used today, but for simplicity I've stuck to Derry in my labels - less typing!
The Royal Irish Academy's Historic Towns Atlas has an edition for the City of Derry / Londonderry. Explore the history and enjoy the maps.