I'm So Lonesome I Could Cry by Hank Williams (click to listen)
I just realized that I've gone more than a year without featuring a song by one of the greatest American songwriters of the 20th century. There are so many great ones to choose from that I even considered doing a full week of nothin' but Hank. But this one will have to do. One of the prettiest, saddest, and lonesome-est songs ever.