Audio Hijack Pro gives you the freedom to listen to audio when you want and how you want. Record any audio with Audio Hijack Pro - it's the cornerstone of your digital audio experience.
adjusts the audio levels within your podcast or other audio file for variations from one speaker to the next, for example. It's much simpler to use. The UI is dirt-simple: Drag-and-drop any WAV or AIFF file onto The Leveler's application window,
Mac OS X only: Freeware app Tangerine analyzes the beats per minute (BPM) and beat intensity of the songs in your iTunes library, then helps you create playlists based on these attributes.
Site for open source offerings MAX and PLAY. Specficially you can use MAX to convert FLAC to Apple Lossless so you can play FLAC files in iTunes. I believe play is a Mac compatible FLAC player but I haven't checked it out yet, so I could be wrong there.