The Victoria Cross is the highestaward for gallantry that can be awarded to British and Commonwealth forces. Wikipedia lists all the recipients by name, and details all awards to date (1,355 in number as of April 2006).
Iain Stewart's Victoria Cross website gives information on every VC recipient who was buried in the UK or Ireland. There are 666 entries giving name, rank, force, date and place of award, date in London Gazette, dates of birth and death, burial location and the present location of the VC itself. In several cases there are also photographs of the headstones. In addition the site provides details of regimental museums holding V.C.s and several articles and news items relating to the award.
Roll of Honour - information from war memorials in a growing number of (mainly English counties), often with photographs of the memorials and additional details, and in some cases photographs, of the men and women named.
The Imperial War Museum's War Memorials Register - "the comprehensive national register of UK war memorials and the names of the individuals they commemorate"
Finding People - links for tracing people or former colleagues in the forces, from BBC Derby.
War-Memorial.co.uk is a subscription service that contains (as of July 2016) "20,000 detailed photographs of more than 1,200 memorials, commemorating over 270,000 people, with their names (and the memorial’s information about them) transcribed and indexed . . it includes a very large number of records from the Boer War of 1899-1902 and WW1 and WW2 but it also includes memorials from as early as the 17th century up to very recent conflicts such as Northern Ireland and Afghanistan".
British War Memorial Project - "A voluntary project to build an online International War Memorial to Service Personnel from 1914 to the present day."
The War Graves Photographic Project aims to "to photograph every war grave, individual memorial, MoD grave, and family memorial of serving military personnel from WWI to the present day and make these available within a searchable database."
Official search facility for finding the will of a soldier who died while serving in the British armed forces between 1850 and 1986.
Details of the National Archives' First World War 100 programme "marking the centenary of the war with an extensive programme, spanning a five-year period from 2014 - 2019 . . . of digitised record releases".
The London Gazette records the promotion of officers and the award of medals and is fully searchable free online.
Asplin Military History Resources - "various materials and information that may be of interest to the Victorian military historian and researcher" - casualty rolls, medal rolls, and more.
The Great War Society web pages provide some very useful historical information and numerous links to related sites.
John Fuller provides details of britregiments, a mailing list for anyone with a historical or genealogical interest in British Regiments (including the Indian Army).
An Unfortunate Region by Peter van den Heuvel & Marco Hoveling - "A website about the Great War battlefields and individuals".
"The Western Front Association was formed to further interest in the period 1914-1918. Its principle objective is to perpetuate the memory, courage and comradeship of those, on all sides, who served their country in France and Flanders..."
The Seven Years' War Website from MilitaryHeritage.com deals in great detail with this 18th century (1756-1763) conflict between Great Britain (allied with Prussia) and France (allied with Austria and Russia).
The Labour Corps 1917-1921 (archived copy) - Ivor Lee's website deals with the history of this little-known unit of the British Army.
The Army Children Archive (TACA) - "established to collect, record and preserve details of the unique aspects of growing up as the child of a serving soldier in the British Army, whether that growing up was done during the seventeenth, eighteenth, nineteenth, twentieth or the twenty-first century."
Forces Reunited - "the largest British Armed Forces Community on the web with over half a million members"
Masonic Great War Project - Roll of Honour 1914-1918 - "based on the 1921 Masonic Roll of Honour 1914 - 1918, which was commissioned and by the United Grand Lodge of England, and the the Peace Memorial built at Freemasons Hall, Great Queen Street which was completed in 1933".
The Battle of Jutland was a naval encounter between the Royal Navy's Grand Fleet under Admiral Sir John Jellicoe and the Imperial German Navy's High Seas Fleet under Vice-Admiral Reinhard Scheer on 31st May to 1st June 1916. – Battle of Jutland Crew Lists Project
The Battle of Britain site includes a listing of "The Few" - "2353 young men from Great Britain and 574 from overseas, pilots and other aircrew, who are officially recognised as having taken part in the Battle of Britain".
Pilots of No. 41 Fighter Squadron RAF, 1939-1945. This (archived)site, which was provided by Steve Brew, "discusses the history of the unit, and includes biographical information on individual pilots, a search engine and a bulletin board. The collection of data and photographs have made this site a very informative and professional tribute to the men who served with 41 Squadron between 1939 and 1945".
The Annals of 100 Squadron (Royal Air Force) is "a record of the War activities of the Pioneer Night Bombing squadron in France during the period March 1917 to November 11th 1918 ......". The site includes listings of officers and other ranks.
Rob Davis provides extensive information on RAF Bomber Command 1939-1945, and offers lookups from his database or all Bomber Command aircraft and crew losses for WW2.
The Midnight Watch - a website "dedicated to the 60 595 men, women and children who lost their lives in Britain during the Second World War (1939-1945) on the Home Front, and to the countless numbers who served in a Civil Defence role during that conflict."
Coleshill House - the Official Home of the Auxilliary Units and British Resistance of World War II. (Includes a Person Search facility.)