TuneWiki, one of our favourite mobile apps, is finally in the App Store in a non-gimped way with full access to your iTunes library (if you close it, it keeps playing through iPod even, like a fake background app).
You get subtitled lyrics (with translations), music maps showing where people are listening to what, internet radio, video search and you can "blip" what you're listening to Twitter, Facebook or wherever kids hang out these days. It's free, and definitely worth checking out. You can also grab it on Android or BlackBerry, if you're so inclined. [iTunes]