The digital collection La 1ère Guerre vue de Paris has been created by Odile Gaultier Voituriez. The collection gives an edition of 1020 letters exchanged during the First World War between two men in Paris, Étienne Bandy de Nalèche (1865-1947), a former diplomat who became the owner and editor-in-chief of the influential Journal des Débats, and Pierre Lebaudy (1865-1929), an industrial entrepeneur, philantrope and art collector. The original letters are mainly kept at the Archives d’histoire contemporaine, Centre d’histoire of Sciences Po in Paris [Fonds Étienne de Nalèche]. The list of other relevant sources and the extensive bibliography merit attention. The letters are posted in a sequence which gives you a day-to-day idea of this correspondance. You can select letters by month of publication.
The digital collection World War I: Declarations of War from Around the Globe has been created by the Law Library of the Library of Congress, Washington, D.C. The collection brings you some twenty declarations of war declared between 1914 and 1918, and additional documents, in particular concerning the American involvement. In some cases the documents are taken from source editions, in other cases you can see the official publication in national gazettes or special proclamations.
You can find more collections of the Library of Congress concerning the First World War at its topical portal.
The virtual exhibition 100 Jahre Erster Weltkrieg [100 Years First World War] has been created in 2014 by the Österreichisches Staatsarchiv in Vienna. You can search among 24 thematic collections which cover many aspects of the First World War and its immediate aftermath. You can look at a chronology for military and diplomatic events, at milestones in daily life and documents related to them, or compare the diary entries of Karl Schneller, an influential officer in the Austrian army staff (Armeeoberkommando (AOK)), and emperor Franz Joseph for a specific date. The exhibition can only be viewed in German.
The digital collection Diplomatic Documents of Switzerland (DDS) is a searchable online version of the scholarly edition of sources for the history of Swiss diplomacy. The search interface of the DDS database gives you refined search possibilities with a free text field, selections from drop down lists and radio buttons. A predefined search for documents for the period 1914-1918 yields some 550 results. You can for example limit your search to terms within certain types of documents, or search for their appearance in the DDS bibliography. There is a special search interface for this bibliography. The links selection brings you to other institutions dealing with Swiss history and culture and their digital collections, and to similar projects elsewhere in Europe. The website and the database of DDS can be viewed in German, French, Italian and English.
The digital collection Western European Theater Political Pamphlet Collection 1894-1918 has been created by Princeton University Library (collection MC 248). The collection contains in 77 boxes items from European countries collected since 1914. Apart from pamphlets in English there are items in French, German, Russian, Italian and other languages. The pamphlets do not only touch upon politics but on many aspects of the First World War and the period immediately before the war. The digitized pamphlets are accessible using an online finding aid. In the left side bar you can click on subjects and time periods which open either an item or a set of items within a record. You can use the general search field for a free text search. It is also possible to view the entire finding aid as a page or to download it as a PDF.
The virtual exhibition Europaeisk krig uundgaaelig [European war is inevitable] has been created by the Riksarkivet og Statsarkivene, the Norwegian national archives. This small virtual exhibition shows twelve telegrams and letters documenting the activity of Norwegian diplomats and politicians during the summer of 1914. Norway was one of the countries that declared themselves neutral during the First World War. The exhibition can only be viewed in Norse.
The digital collection Deutsche Beuteakten zum Ersten Weltkrieg [Looted German records concerning the First World War] is a project of the Central Archive of the Ministry of Defense of the Russian Federation (TsAMO RF). The documents in this collection, divided over 475 units with some 36,000 pages (Bestand 500, Findbuch 12519), stem from several German military authorities, in particular the Generalstab and the Obere Heeresleitung, and from a number of ministries. Among the documents are unit diaries (Kriegstagebuch) and other front reports (Gefechtsberichten), diplomatic documents (nrs. 321-324 deal with the Russo-Japanese war of 1904/05), some 150 maps, some 80 personal dossiers, and a wide variety of other documents, almost all dating from the period 1910-1919. You can search using the free text search or the index search for labels such as number, year, page, and language. This digital collection can be viewed in Russian, German and English.