Databases

• House of Commons Parliamentary Papers
  Papers from 1685 - 2009.  No Hansard.
• Public Information Online
  Parliamentary papers from 2006/7 onwards.  Includes Westminster and devolved parliament papers.

• Tutorial
  How to search for British Official Publications.  Lasts @ 6 minutes
  

Parliament

• UK Parliament
• Parliamentary Business
  For Commons, Lords, Bills and Legislation information.
  
• Committees
• Weekly Information Bulletin
• Commons Library Briefing Papers
  Research papers and notes on all kinds of subjects.
  
• Search Parliament webpages

Hansard

• Hansard Online
  Text, Commons debates from1988 and Lords from 1995
• Historic Hansard
  Commons
  
• Historic Hansard
  Lords
  

Devolved Governments

• Northern Ireland Executive
• Scottish Parliament
• Welsh Government

Government Departments

•  Directgov's A-Z of government departments

Historical sources

•  Cabinet Papers 1915 - 1980
  Access to more than half a million pages of minutes and memoranda.
  
• Parliament Rolls of Medieval England
  Official records of the English parliament from 1272 to 1509.