Playing with sound files is something not all of us aspire to do in any greater detail than clicking "Buy Now" in iTunes. But this is one of those cool Mac niches that is filled with possibilities you might not have thought about before.
For instance, have you ever wished you could easily record a phone call for a job interview? How about automatically record your favorite radio program from the Internet, even if it's on in the middle of the night? Ambrosia Software's WireTap Studio, recently updated to version 1.0.8, is an inexpensive and efficient way to record and edit pretty much any audio that you can play on your Mac. You can select any combination of software application (Skype, for example) and hardware device (say, your Mac's microphone), and record the output quickly and easily.
Once you're set up, simply click record, and the end result will be a clean recording of your conversation for your job interview, podcast, custom playlist, or iMovie project.
WireTap Studio offers a complete set of editing tools and lets you export to a variety of compressions and audio formats. Possibly my favorite feature is called LivePreview, which is a button that allows me to hear what my audio will sound like in different formats and levels of compression, before I start recording. This is great when your needs require the file to be under a specific size, yet you want the best quality possible.
WireTap Studio costs $69 for the full version (link above is to 30-day demo), but if you have specific recording needs, this is the perfect software for the job and may be worth the price.