On OS X, how can I see which song/stream/... is playing in iTunes? On OS X, how can I see which song/stream/... is playing in iTunes?

I don't want to go to the messages dock on the right side of the screen, just want to see the currently playing title in iTunes itself.

The reason is that once every while when you double click an mp3 file in Finder, iTunes will play it, then continue with some web-stream. Not nice when you are on pay-by-the-kilobyte tethering...
Unfortunately, even the most recent release of iTunes doesn't have a very good method for this.

You could use the Mini-Player option, either from the Window menu, or toggle with option-command-M, but that is designed for album art - and won't show you the track info unless you mouse over it.

There are plenty of 3rd-party utilities, however.  I still use Bowtie for an inobstrusive floating desktop status, there are also others that can display your current track in the menu bar or via Growl, Mavericks' Notifications, etc.