Mac-based iTunes users might be interested in "TRAKART" - a plugin that we've just got word of. It's a visualisation tool which dynamically generates music videos for songs based on their lyrics.
It's been built by Belarus-based developer Belprog and accesses LyricsWiki for any song you play. If it's in the database, then it combs through and turns those lyrics into search terms if they're about a certain character count.
It then searches public images on Flickr based on those keywords and displays the images before your eyes. If the lyrics aren't in the database, then it will pick random keywords instead.
Currently it's Mac-only, and works with iTunes 7.4 or higher. The team's planning a full release (on Windows too) for this summer, but for the moment it's in Alpha - expect a few bugs. You'll need to visit the developer's website and provide your email address to get a download link.