Not technically one song but Sum 41 has a trilogy of songs called A dark road out of hell, which is collectively 11 minutes and 40 seconds according to Itunes.
Metallica - One [7:25]
The version I have is like 3 seconds longer.
Itunes adds 3 seconds onto the end of songs. The Vengaboys have a song called Opus 3 in D#, which is 7 minutes and 11 seconds long on a regular CD player. On Itunes, it is 7 minutes and 14 seconds long.