The governments of the major participant's in the two world wars maintain their cemeteries in Europe through public or public and private funding. Their websites provide information about the scope and responsibilities of their organization and usually provide a search capability to locate a particular individual's grave.
American Battle Monuments Commission lists American overseas cemeteries containing graves from participants in the First or Second World War and provides a search feature to location specific individuals. Although originally focused upon construction and maintenance of America's overseas cemeteries and memorials, the commission has begun presenting historical overviews on its website.
Commonwealth War Graves Commission lists British Commonwealth cemeteries contain soldiers of British, Canadian, Australian, New Zealand and South African origin who died in the First or Second World War. Frequently these cemeteries also contain the remains of enemy combatants who died in local engagements. The web site offers a search feature to locate the grave of a specific individual.
German War Graves Commission (Volksbund Deutsche Kriegsgräberfürsorge) lists German war graves from both world wars. It offers a search feature for specific individuals, however since the burial locations of many German sodliers were never identified after the end of hostilities and because many German soldiers' bodies were not identified before burial, the database is far from complete.
Unfortunately, a searchable database currently does not exist for French cemeteries. Inquires should be directed to the Le Ministere des Pensions at:Ministere des anciens Combattants et Victimes de Guerre
Official government websites provide information about their military units' engagements. Frequently these reports present a level of detail not otherwise easily obtainable. They may be fully downloadable as pdf files.
The Imperial War Museum has the most extensive collection of First World War photographs, which can be viewed at their offices in London. Selected, digitized photographs may be viewed on line. The national archives of the United States and Canada permit access to their photograph, video, and cartographic records. Canada and Australia have digitized selected items that can be viewed on line. The United States does not offer on line viewing at this time. Requirements for personal or commercial use of the photographs varies and should be reviewed with the appropriate staff.
All French Regions (the 22 governmental jurisdictions that comprise France) and most cities and towns have an Office de Tourisme or Syndicate d'Initiative. They can provide a multitude of pamphlets, itineraries, special sites and hiking, cycling, or driving maps (usually the latter for a small fee). Generally, they do not provide reservations for accommodations.
Many individual maintain websites that contain information about specific war, battle, or units. These website frequently offer information and personal observation not generally available from government-sponsored organizations. Some of the better sites are listed below.
One of the best First World War sites on the internet is maintained by a Dutch enthusiast who goes under the pseudonym of Pierre le Grande Guerre. He specializes in providing information on specific battlefields and he presents maps and historical and contemporary photographs of the selected locations.
The World War II Database holds thousands of biographies, photographs, diagrams of ships, planes, and weapons, book reviews and maps, among other entries. Access is unrestricted and provides an enormous resource for Second World War materials.
Traces of War provides map-based references to thousands of visitable sites all over Europe mostly but not exclusively related to the Second World War. Found by Dutch enthusiasts, the locations usually provide photographs and a brief description of the artifact. Histories of engagements and biographies of leaders and service personnel are also available.
Internet forums such as Axis History Forum, Great War Forum, Military History Online, and World War 2 Talk are supported by experts in their individual fields and offer the opportunity to ask very specific questions or participate in discussions on military issues. Registration is generally required to participate.
A number of authors have written books on specific subjects. Two that I can recommend are David Homsher's American Battlefields of World War I: Chateau Thierry - Then and Now, which presents the American force's story at the battle of Chateau Thierry and, at the other end of the spectrum, Nancy Rial's family experiences in World War II in Alan's Letters.