Kid Rock's "All Summer Long" is a mashup of "Werewolves Of London" and "Sweet Home Alabama." The album it came from was released in October, 2007, but they held off until summer, 2008 for a more seasonable release.
"Friends In Low Places" by Garth Brooks was written by two Nashville songwriters after a meal in a local restaurant. One of them forgot his money, but said not to worry, "I have friends in low places. I know the cook."
"Bittersweet Symphony" by The Verve samples an obscure orchestral arrangement of the 1965 Rolling Stones song "The Last Time." The Verve had to sign away most of the royalties before they could release the song.