I don't know if you guys have seen this before but I couldn't believe it when i found this little gem searching the web. Take a look:
Minilyrics site:
http://www.crintsoft.com/I don't really know if there are other apps which do the same job but what i really liked is obviously it has a plugin for Media Center.
I didn't found any reference to this searching through the forums so i thought someone else could be interested in trying it as well.
Basically what it does is display synchronized lyrics along with song playback. It acomplishes this with simple embedded time tags on each "lyric phrase" inside a plain text file (named LRC format).
Of course, you could spend all your life doing this manually with the included editor but to help you start, it lets you download lyrics in the mentioned format from an extensive database which is fed by users like you or me. You can also download simple TXT files (no timing, just lyrics). Again, you have an editor to correct lyrics or incorporate/correct the timing.
As you play a song it pops a separate window which you could just put "always on top" and set to show big fonts to use MC as a karaoke machine (without original vocal removal of course). You can tweak on the window opacity if you like. This windows features also buttons to control MC's playback.
Speaking again of the online search, the program tries to best match the song you're looking for based on current name and artist tags which leads it most of the time to automatically find the lyrics ON DEMAND, which means that if you have a dedicated internet connection you have to do nothing else but push PLAY and start singing. Whenever the program feels confused about which song it is, it still lets you choose the best match based on user ratings for lyrics and timing accuracy. I found this particularly useful. If the program can't find a LRC lyric then perhaps you can still find a TXT one. Practical difference between both formats is that on playback you have to manually scroll TXT based lyrics, which is not what we'd want.
The app has interesting modes to fade in/highlight the current playing lyric line, showing several lines of the lyrics if you want to anticipate the content. Best mode for me is "Double line" mode as it's screen space friendly and highlights just the current line and leaves the other line for upcoming content.
The only con i've found so far is that even it has the option to let you store tags in the lyrics ID3v2 tag it doesn't seem to update it (perhaps someone could test this too), but yet it allows to save lyric files either in the mentioned LRC format or plain TXT files (only lyrics, no timing info) in a separate directory so for me at least it represents no problem.
So to you ... sing along friends, this could be the plugin you were searching for. Personally i loved it as is.
Cheers!