Across Directgov you'll find information and services on tax self assessment, jobseekers' allowance, family tax credits, child benefit, road tax, disability living allowance and more.
http://www.direct.gov.uk

The United Kingdom Passport Service (UKPS) site aims to assist new applicants and existing passport holders by providing information and online facilities for all aspects of application, renewal and amendments of passports for British nationals resident in the UK. For non-UK residents please go to the Foreign and Commonwealth Office page.
http://www.ukpa.gov.uk

The OFT is responsible for making markets work well for consumers. We achieve this by promoting and protecting consumer interests throughout the UK, while ensuring that businesses are fair and competitive.
http://www.oft.gov.uk

HM Customs and Excise is a Government department with responsibility for collecting billions of pounds in revenue each year in VAT, other taxes and customs duties. We also have a vital front-line role in protecting our society from illegal imports of drugs, alcohol and tobacco smuggling and tax fraud.
http://www.hmrc.gov.uk