[Macworld.com]

Use a handy trick to listen to a music file without adding it to the iTuned library. [more]

[elseedee]

Couldn't you simply open the file with QuickTime Player?

[sfn]

Rob, I think you mean "not added/copied to the iTunes Music folder" instead of the "iTunes Library" because regardless of whether or not you drag with the option key down it is added to the Library in the Source pane of iTunes. The file is just not also copied into the user's selected iTunes Music folder. If you delete the playlist it will not delete the file from the Library UNLESS you again hold the option key down while deleting the playlist. You can also bypass the warning by holding option+command.
This is on iTunes 6.0.4.
-sfn

[Somynona]

I just use Quicktime Player.

[michaelb]

Another vote for QuickTime Player. Just drop the file onto the shiny blue Q logo in the Dock.
QuickTime can play more types of media than iTunes anyway, and export them to iTunes-friendly formats if necessary.

[alauser]

On my system, at least, if I do Get Info on a file in the Finder, one of the available panes is Preview, which allows me to play a sound file without getting into iTunes or any other application.

[Bruce8]

Ditto. I use QuickTime Player to check out audio I DON'T yet want added to iTunes (at least, not until I have previewed and decided).
And, it is more efficient to use QT, because you only need one drag file step to the QT icon (wherever you have it - mine is in Dock and DragThing panel), and QT gives you the same forward, back, pause kind of controls.
Drag multiple files at once to QT, which will open multiple little QT windows, one for each audio file.
The tip about unchecking then rechecking the 'Copy files to iTunes Music folder' is really more about how and where one chooses to have their audio/music files moved and stored. With that check mark on, the audio file is actually copied and moved to the users home music location.
For myself, I have set up my own music folder located on a different partition volume, and have my own system of audio music folder organization, so I leave that always unchecked because I do not want any of the audio/music files being automatically copied to default home folder.

[Wiggus]

This is a great hint. I like to use iTunes to make mp3's of recordings from ProTools to mail to friends, but don't want to add the huge .aif's to my library, then have to turn around and delete them. The only drawback to using Quicktime is the lack of an equalizer (I have iTunes calibrated for both my small satelite speakers and my studio monitors). But this is probably not an issue for most people.

[Nobody]

Holy heck, I can't believe the Macbook Pro ad that was embedded in this story. Was this ad really created by Apple? It's enough to induce an epileptic fit.
Actually, the same goes for the Crucial ad that I am seeing at the top of this page. Can Macworld please introduce a policy against animated ads? They are so horribly nauseating. I'm not sure how they help advertisers.