I just found this link on the website of my local NPR station. It's a blog by the grandson of a British WWI soldier. He's transcribed all the letters his grandfather wrote home from the war, and is posting each of them exactly 90 years to the day after their original postmarks. I haven't gotten to read it yet, but it looks like a great opportunity to follow a soldier's story in close to real-time, as his family did almost a century ago. The first letter went up on Feb. 7.
http://wwar1.blogspot.com/