You still need to get an invitation to use Songboard, but it seems to have a pretty clean interface to show music videos with highlighted words as they are sung. It doesn’t have a way to record your singing, and you have to sign in using Facebook (though you can get access to a number of them without signing-in), but it still might be worth checking-out.

I’ve added it to The Best Online Karaoke Sites For English Language Learners.