There don't appear to be any dedicated competition sites based on song lyrics. This is probably because, paradoxically in view of the fact that the web lends itself perfectly to the train-spotter mentality in all music fans (and I confess I'm as much a fan as anyone else!) which means there are loads of lyric sites, there are copyright problems in trying to obtain permission to use lyrics on a site for commercial gain - hence the absence of any sites on the Net. The only solution is to make up your own, and invite a few friends round for an evening of nibbles, drinks, and yelling "I know it ...I know it ... it's gone!" at the tops of your voices!