Songbird is a free, iTunes-like offering with most of the features you would expect.  It is open-source and available for Win/Mac/Linux.  iPhone integration isn’t there yet, but other features make this a unique and wonderful music discovery tool.

Built on the Mozilla Firefox framework, Songbird offers myriad add-ons to enhance your listening experience.  In addition to things like MASHtape (which displays information about the artist currently playing) and integrated concert listings, the Songbird web browser is just plain built for finding digital music.  When you open a webpage, the browser collects direct links to any digital music files and lists them in a separate window frame for convenient download.  Even better, you can set up feeds for individual blogs and Songbird will automagically download new tracks to your library as they are posted.

Couple this with Simplify Media, and you can be listening to new tracks almost instantly from anywhere.

Simplify Media is a music broadcasting/sharing application that lets you access your entire digital music collection anywhere (at work, on your second computer, and on your iPhone).  It’s gotten a ton of good press, but I don’t think I know a single person (other than me) who actually uses it.  And that’s a crime.

All you need to do is download a small application to your computer (they have Windows, Mac and Linux versions).  It will scan your local machine for audio files, and that’s pretty much it.  Download the same app on another networked machine, enter your username and password, and you’ll have access to your entire music collection.  (They also have an iPhone app, which lets you access your entire library over wifi or 3G.  Buffering has been lightning fast for me, even at 3G speeds, and I’ve even gotten access underground.)

But here’s the best part:  you can also share your music library with thirty – that’s 3-0 – of your closest friends.  Just exchange passwords, and you will have access to their music anywhere, too.