The BBC will be covering World War One in great detail over the next four years. They've already started, with podcasts, interactive guides, online courses, programs new and old plus much, much more. Perhaps it's best to start at the beginning, with Professor Margaret MacMillan's Countdown to World War One (podcast link) or the account of her fellow historian Christopher Clark, Month of Madness. Of course, how the war started is still contested by historians, as recounted in The Great War of Words. The latter two are also part of the main WWI podcast. Or you can dive into the Music and Culture section, go through an A-Z guide or look at comics drawn by modern cartoonists.
Voices and Music of World War I and Voices of World War II: Experiences From the Front and at Home both feature spoken word, sheet music and songs galore (all audio RealPlayer). The Great War site has plenty of stuff, but the core is the collection of songs, anti-war, patriotic, France-themed, Kaiser-knocking and so forth. The WWII site also has a whole bunch of music, demonstrating the changing mood of the US, from conflicted feelings about the start of the war to conflicted feelings about the atomic bomb. Among the artists are Nat King Cole, Leadbelly, Benny Goodman and Fats Waller. But in addition the wonderful songs there are newscasts, speeches, propaganda and other radio broadcasting of all kinds.
Gallipoli is one of the most famous battles of World War I. Fought in on a Turkish peninsula in 1915 it was, like most Great War battles, a huge waste of life and largely fruitless. Jul Snelder's site has a wealth of information, the causes, history and aftermath of Gallipoli, the slang of the ANZAC forces, placenames in both English and Turkish, interesting little factoids, how Allied troops used subterfuge to hide their evacuation, the Turkish perspective, pictures of the battlesite today juxtaposed with old photographs, a mini-travel guide to Gallipoli and much more. One of the most famous units at Gallipoli was the Australian 12th Light Horse Regiment. To learn more about this type of unit, responsible for the "last successful great cavalry charge" two years after Gallipoli, I direct you to the excellent website of the Australian Light Horse Association, where you can learn anything you might reasonably want to know about the subject.