Here are some of my favourite UK genealogy sites:

• Certificate Ordering Service
• GENfair
• GENUKI
• Family Search (inc. IGI)
• Leicestershire & Rutland FHS
• Rootsweb
• My Wordconnect tree at Rootsweb
• Society of Genealogists
• Ancestry.co.uk
• Reunion (Family Tree Software for Mac)
• National Archives
• Commonwealth War Graves Commission
• 1911 Census
• Proceedings of the Old Bailey
• FreeBMD

And one more, courtesy of the children of After School Care Programs:

• Home Advisor: History at Home