I found this site online called Letters of Note. It posts letters from well-known folks. Some, like the one from Kurt Vonnegut, writing home from Europe to his parents after surviving capture by the Germans and the fire bombing of Dresden, are touching. Some are hysterical, like the one from Iggy Pop about America and the music scene here ("A country of midgets ruled by Dwarves"). For straight up vitriol, though, nothing beats this one from Hunter S. Thompson to Holly Sorenson, Production Executive at the indie movie studio, The Shooting Gallery.