This gateway site and virtual reference library offers free access to a vast genealogical collection. This is a great site for research help and detailed information with data arranged geographically. There is regional page links for England, Ireland, Scotland, Wales, Isle of Man and the Channel Islands. These then link to dedicated pages for each county that contain detailed, categorised information with links to online records.
TIP: This site is a must to visit. Check out the Search GENUKI, Gazetteer, Church database, Societies and Getting started Quick links.