To anyone looking for a simple solution to MP3 file management and playing... please read this and see if it sounds useful.
Apple's iTunes is a superb bit of software, but it is designed to be more of a consumer-oriented tool than you may like. That doesn't mean underfeatured, but it does mean it prefers to take control of file management a little more than you may be used to. It doesn't behave quite like a traditional Mac app, it behaves like a new-generation consumer-focused 'iApp'.
If you're happy with it, that's fine: it is, like I said, a very good bit of software.
If however you want something that's more smoothly integrated with the Finder in almost every way, behaves like a regular Mac app, and lets you use tracks from wherever without insisting on trying to maintain a central library - try Audion, from Panic Software:
http://www.panic.com/
Yep, it is commercial (but not expensive). No, I'm not from the company.
As far as I'm concerned, it is a more flexible and professionally-oriented MP3 player. We use it in MacUser magazine's office.
Keith
technical editor, MacUser magazine
http://www.macuser.co.uk/