If you've been looking for a way to hijack MP3 streams, just call the
Rogue Amoeba. Hijacking MP3 streams is only one of the specialties of
Audio Hijack from the Rogue Amoeba studio.
Audio Hijack will intercept any audio stream running through your computer and allows you to inject your our effects. This includes audio from any application and any Internet audio source. Customize your Quake game or record NPR. I bought a copy of
Audio Hijack Pro which has a number of nice features over the free version including enhanced timed recording, hijacking of multiple streams simultaneously, plug-ins, and the ability to save DSP settings. I used it to grab over an hour of streaming MP3s, loaded the hijacked file on my iPod, and listened to it at the gym tonight.
Warning: Mac OS X only.