Amergin, I'm with you on the John Williamson stuff. I'd add his and Pixie Jenkins' "Teach Me To Drive" to your list.
For Christmas I'd want to hear Frank Kelly's "Twelve Days Of Christmas". And then there is Mike Agranoff. His "Ten Ton Molly" and the one about the song writer and the character in the song having a fight (can't remember the title just now) are both absolute screams.