It's like Firefox, but for music.
I've been anxiously waiting for Songbird to release on Mac OS X, ever since I found out that they had hired a Mac developer. Until now, they had only been releasing on Windows.
Now they're releasing nightly builds, on Windows, Mac, and Linux. I'm really happy about this! I'm currently downloading the Mac nightly build from 06/30/06, and I'm going to try it out as soon as possible. I hope it replaces iTunes. Right now I'm using a combination of iTunes and the c* music player (cmus) to play all the files I have of various formats. cmus still has very serious issues on Mac OS, making it pretty much useless, and I don't have the skills to fix it. Songbird looks promising, though.
UPDATE: I tried it, and it's crap. Wait a long time before it's usable.