The National Archives of England, Wales and the United Kingdom has one of the largest archival collections in the world, spanning 1000 years of British history, from Domesday Book of 1086 to government papers recently released to the public.
http://www.1901census.nationalarchives.gov.uk

Oldschoolmates.co.uk is a huge database which at the moment holds over 38,000 Schools, Colleges and Universities. Registered users will be able to find their old schools and contact their old mates. 1) Choose your country. 2) Choose your county. 3) Choose your School/College.
http://www.oldschoolmates.co.uk

For more than 200 years, Debrett have been the recognised experts in English, Irish, Scottish and Welsh genealogy with the publication of Debrett's Peerage and Baronetage. Let us now help you in tracing your roots. Bring your family history to life through our range of genealogy and research services.
http://www.debrettancestry.co.uk

Census Searches provides a service to the legal profession by obtaining copies of birth, marriage and death certificates and obtaining copies of wills, grants of probate and letters of administration.
http://www.census-searches.co.uk

Register to catch up with old friends and reminisce about the old days. Search by name, school, university, team, club or work place. With over 16 million people listed and sites across 10 countries, Friends Reunited makes it easy to find old friends and discover what they're up to now.
http://www.friendsreunited.co.uk