Lyrics Training is an easy and fun method to improve your ability to understand English through the music and lyrics of songs. Choose a song (3 levels of difficulty), select a game mode (Beginner, Intermediate or Expert), watch the clip, and fill in the gaps in the lyrics.
I'm impressed! The choice of songs is limited at present (no Britney Spears or Lady Gaga!), but the interface works really well—the clip is even paused automatically at the end of each line. In 'Expert' mode, all the lyrics are blanked out, so this would challenge even advanced learners.
To see all the songs available at each level, choose a level, and click on the magnifying glass in the search box, leaving the search box blank. There are around 100 songs in all.