BBC.co.uk
Recommend or find an architectural walk in the UK.
http://www.bbc.co.uk/radio3/architecture/archwalks.shtml

English Heritage
Find out more about London's listed and Blue Plaque buildings.
http://www.english-heritage.org.uk/

Great Buildings .com
Lists buildings in London that are worth a second look.
http://www.greatbuildings.com/places/london.html

Historic Royal Palaces
Official guide to royal abodes in London.
http://www.hrp.org.uk/

London Architectural Diary
News and information about London's architectural scene.
http://www.londonarchitecturediary.com/

London.gov.uk
A brief guide to the capital's architectural history.
http://www.london.gov.uk/london-life/environment/architecture/architecture-highlights.jsp

London.gov.uk
Provides a brief overview of architecture in the city, both old and new.
http://www.london.gov.uk/london-life/environment/architecture/index.jsp

National Trust
Search for historic buildings and gardens in and around London as well as the rest of the country.
http://www.nationaltrust.org.uk/

Open House
Every year, over 500 buildings open their doors to the public for free, turning the capital into a living architectural exhibition.
http://www.londonopenhouse.org/