Office of the Immigration Services Commissioner
Responsible for ensuring that persons seeking immigration advice and immigration services are treated fairly, honestly and receive competent fit advice.
http://www.oisc.org.uk

The Home Office
Site for the UK government department dealing with law, public order, public safety, immigration, fire, passports, prisons and the police among others. Includes detailed information on a number of issues including the Crime and Disorder Act.
http://www.homeoffice.gov.uk

UK Passport Agency
The executive agency of the Home Office which is chiefly concerned with issuing and servicing UK passports to British nationals who are resident in the UK.
http://www.ukpa.gov.uk