If you are of Irish descent, or doing research on lines from Ireland, Library Ireland has posted A Topographical Dictionary of Ireland online. Library Ireland is a great resource for researchers (and it’s free), offering a large number of out-of-print books online.
SEVERAL COUNTIES, CITIES, BOROUGHS, CORPORATE, MARKET, AND POST TOWNS.
PARISHES, AND VILLAGES,
HISTORICAL AND STATISTICAL DESCRIPTIONS;
ENGRAVINGS OF THE ARMS OF THE CITIES, BISHOPRICKS, CORPORATE TOWNS, AND BOROUGHS;
OF THE SEALS OF THE SEVERAL MUNICIPAL CORPORATIONS:
DESCRIBING THE ELECTORAL BOUNDARIES OF THE SEVERAL BOROUGHS, AS DEFINED
BY THE ACT OF THE 2d & 3d OF WILLIAM IV.
BY SAMUEL LEWIS.
This is a neat publication with a lot of historical background for the various counties/cities.