Mac: Song Announcer is a utility that works with iTunes to announce the artist and name of the song that's about to play, lets you control playlists and playback from the menu bar or even your web browser. The app uses text-to-speech to speak the song info to you so you never have to switch to iTunes to see what's playing.
In addition to announcing the song title and artist audibly before the song begins, Song Announcer also starts a local service that lets you control iTunes from your web browser. If you spend all day in a web browser, you can use Song Announcer to keep iTunes up in a tab so you don't have to switch to the app.
If you prefer, you can use Song Announcer's menubar utility to switch playlists, start and stop playback, or display song lyrics when the song starts playing. Song Announcer also supports Growl notifications, so even if you're working in another app you'll get a pop-up alert with the album art, the song name, the artist, song length and iTunes rating in it.
The app is a great way to hear what's about to play without keeping iTunes open in the background, or to have a virtual DJ announcing each new song to you as it starts. It's Mac-only, and available for $2.99 in the Mac App Store.