Excellent site - guide to architecture in US and Europe with useful details on how to visit them also has pdf guides to London, New York, Paris, Switzerland
Extensive database of Great Buildings around the world Ð often with visiting details and pictures.
UK-wide architecture event in June every year Website has ÔSense and the CityÕ walking tours and maps for Birmingham, Bristol, Liverpool, London, Manchester, Newcastle/Gateshead.
Annual London event every September where over 500 buildings are open to the public Ð but also offer tours throughout the year
UK-wide event every September including Contemporary Architecture
Guide to London Architecture
Organise Architectural Tours
European Network of Architectural Guides
Online Tours & Maps of Edinburgh Architecture
US Company specialising in organising architectural tours
Details of Architectural Tours and Trips can be found on their Event Listing.
See also Twentieth Century Society Walk and Tour Notes http://www.c20society.demon.co.uk/docs/publications/london.html
Click "Properties" for detils of Lutyens buildings open to the public (plus a self-guided walk of Lutyens properties in London)
Over 200 buildings and gardens in UK
Searchable database of places to visit
Part of V&A Art Deco Exhibition website