With PlaySound CMM installed, if you control-click on an AIFF sound file, one of the items in the contextual menu will be 'Play Sound'. Just select 'Play Sound,' and the sound will play. Click the mouse or press a key to stop the sound. The Play Sound items won't appear if you control-click on a sound file in any format other than AIFF, or on any file that's not a sound. (But, as always, you can play System sound files by double-clicking).
PowerPC, MacOS 8.0 or later