Ancestry.co.uk has begun adding World War I British Army service and pension records, starting with 100,000 records for A and B surnames. If your ancestor's name began with "zed," you might have to wait until 2008.
They reveal intriguing personal details, such as how Pte Thomas Beedham, a 34-year-old fitter from Leicester, was "admonished" and fined four days pay for absenting himself from a draft on Aug 28, 1916. The forms also show how Pte John William Ballinger, of 1bn Manchester Regiment, had a "distinctive" scar on his right leg and how one soldier was almost 64 when he fought. [Link]To the question "Will you still need me, will you still feed me, when I'm 64?" the British Army evidently answered, "So long as you fit the uniform."