In my official work capacity as a journalist, I'm the exec. producer of nationalpost.com so excuse the shameless plug. We've been running blog posts from Canadian marathoner Robert Kent who is doing the Marathon des Sables, a 243K run in the desert! Here's where you can read his dispatches. He finished the 'marathon' portion of the race just the past day and has 17K to go.
He also has this crazy ability to hide lactic acid from his body.