Tossing my own personal favorite onto the pile of songs about the recently resigned Donald "Spit Bubbles" Rumsfeld, here is the Gate 5's Rumsfeld-centric WFMU hit from the Fall of 2004, "Unknown" [Download MP3]
This song is originally from the band's "Rummy" EP, on the Dramaphone label. From the CD insert: [The Rummy EP was] without a doubt inspired by Hart Seely's column at Salon.com in the Spring of 2003 "The Existential Poetry of Donald H. Rumsfeld". Lyrics are based on official transcripts of press briefings given by Secretary of Defense Donald H. Rumsfeld, as posted by the Department of Defense of the United States of America on its official website."
A newer version of the song is available on the "Rummy Redux" EP, which you can get here. Big thanks to Alvin Case at Dramaphone!