TuneWiki is a free fun music app that gives a peak at what is popular around.

TuneWiki’s chief charm is the ability to scroll lyrics karaoke-style as a song plays, whether the music is coming from your phone’s built-in payer or from an internet radio station. No more excuse for singing “’Scuse me while I kiss this guy,” during “Purple Haze.” The lyrics are added wiki-style by users, so you might spot some howlers.
Beyond that, the app lets you look at what other users are listening to around the world, or to see what the most popular songs are with Tunewiki listeners. You can see what people near you are listening to, or, on the Android version, you can see where other people in the world are listening to the same song you are at that moment. Songs can be purchased through the site, forwarded to friends, and (except on the Blackberry) you can post what you are listening to on Twitter and Facebook.
There are still bugs to work out and developers are still adding features. They promise that within weeks you will be able to set up a network to see what your friends are listening .

For more, see NYTimes.com