A few years ago, I found a nice tool for iTunes/Mac OS X called PearLyrics. It would monitor what was playing now in iTunes, connect to various Internet servers and search for the lyrics of the current song. It was efficient & quick.
Long story: the record industry giants "didn't understand" and felt this tool was jeopardizing their IP, legal saber rattling ensued, etc. Supposedly it's all cleared up now, but it's worth noting PearLyrics' "hit rate" has dramatically diminished. "Sorry, no lyrics found" is the typical response; successfully finding lyrics happens about 1 time in a dozen.
I took a look at other similar software, and found even Harmonic (which is linked from Apple's downloads site) seems to have extraordinary difficulty finding lyrics for the majority of songs in my library. Makes me wonder what's changed on the Internet behind the scenes. And who made those changes.