GENUKI – a virtual reference library of genealogical information for the UK and Ireland, a non-commercial service maintained by a charitable trust and a group of volunteers. Click on England to home in on counties/parishes or by topic.
A Vision of Britain Through Time – from 1801 to now, including maps, statistical trends and historial descriptions. Search by place name.
UKBMD – lots of links to historical and genealogical information for UK.
List of Registration Districts including changes 1837-present day.
Online Genealogical Index – Enter the country, county, town and approximate year, and OGI will check its database of 403,128 online data sets and list those that hold data for that town and year.
Victoria County History – an ongoing project (since 1899) to write the history of every county in England.  You may find something useful for your research here.
Cyndi’s List – links to thousands of genealogy databases and websites, international.