iCommune is an application that extends Apple's iTunes to share music over the network. It allows you to share the music in your iTunes library and access other iCommune music collections. iCommune music collections appear as playlists in your iTunes window. You can browse through them, and choose to stream or download the music they contain.
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing to fetch them if they aren't available in iTunes. If you don't want to set all your lyrics manually, you can use an application like "Harmonic".