General links for British History
Spartacus, a rich source of information on British history
Wikipedia offers a very useful year-by-year context : ... 1899, 1900, 1901, 1902 ....
Dictionary of the History of Ideas
Miscellaneous dictionaries (click on "history")
The Institute of Historical Research website
BBC History pages
The History Today website

General Links for the British Empire
The  entry for "British Empire" in the Wikipedia and the Concise Encyclopedia Britannica
Paul Halsall's Internet Modern History Sourcebook offers some primary sources on the subject of Imperialism
The British Empire, an internet gateway, maintained by Jane Samson of the University of Alberta
The Commonwealth Institute, London
The Institute of Commonwealth Studies, especially their British Documents at the End of Empire Project
The British Empire & Commonwealth Museum, Bristol
Project South Asia, a site run by Karl J. Schmidt at South Dakota State University

Specific links for the British Empire
The 1924 British Empire Exhibition, a site maintained by Michael Fuller
The Spartacus Internet Encyclopedia on the slave trade
A site on American imperialism
"The White Man's Burden and its critics", a site on Anti-Imperialism in the United States 1898-1935, edited by Jim Zwick
A (very) few comparative statistics
A site to celebrate Lord Kitchener
A review by Keith Windschuttle of The Oxford History of the British Empire (1999)
Text of the Statute of Westminster 1931
Page concerning the UN and Decolonization
History of Imperialism, at The Net's Educational Resource Centre  

Boer War : eyewitness accounts and contemporary texts 
Full text of Kipling's works
Full text of Joseph Conrad's short stories "Heart of Darkness" (1901) and "An Outpost of Progress"
Full text of war correspondent Stanley Mckeown Brown's narrative With the Royal Canadians (1900)
Full text of Erskine Childers, In the Ranks of the C.I.V.
Full text of a diary by mounted infantryman Private Collett of 2nd Middlesex Regiment, South Africa 1899-1901.
Full text of The Great Boer War by Arthur Conan Doyle (1902)
Full text of Gandhi's The History of Satyagraha in South Africa (1924)
Full text of J.A. Hobson, Imperialism. A Study (1902)
The diary of Private John Jackson of the Green Howards 1899-1900
Full text of Lady Butler's Native Races and the War (1900)
Transcription of the personal diary of “Private Walter Putland”, 1900-1902
Memoirs of Katherine Louisa (Oswell) Nealon, Nursing Sister at Ladysmith, 1900
Full text of Sol Plaatje's Native Life in South Africa (1916)
Full text of Deneys Reitz' Commando
Full texts of Olive Schreiner's  The Story of an African Farm (1883)  The Political Situation (1896) and  Trooper Peter Halket of Mashonaland (1897).
 

Other Boer War Links
Stanford University's extensive links to South African history
Extracts from the London Illustrated News, December 1900
The Anglo-Boer War Museum in Bloemfontein
The (British) National Army Museum
The Anglo-Boer War Study Group of Australia offers a well-illustrated Centennial Exhibition
NZ participation in the war
The Canadian Anglo-Boer War Museum
The Pine Tree Web, a rich site about Baden-Powell, the hero of Mafeking
A short summary of the war, in French, at Hérodote
A good review of the BBC radio retrospective on the war, from the World Socialist Web Site
 

Journals
Commonwealth (Chevreul, Gerland) Index of articles
Cultures of the Commonwealth (Chevreul, Gerland) Index of articles
History in Focus, journal of the IHR
Journal of Commonwealth & Comparative Politics
Journal of Commonwealth Literature (Gerland)
Journal of Commonwealth and Postcolonial Studies
Journal of Imperial & Commonwealth History
Jouvert
Kunapipi (Gerland)
List of Commonwealth Literary Journals (compiled by Commonwealth Institute)
World Literature written in English (Gerland)
South African Military History Journal

Research Groups
Société d'études des pays du Commonwealth (SEPC)
The South African Military History Society