Basic overview of what the tool does:

You can record any audio. Record from applications like iTunes, Skype, or DVD Player. Record from microphones, Radiosharks and other hardware. If you hear it, you can record it. –rogueamoeba.com

Recording any audio: VoIP Recording, Record all Audio to one file with system audio, Application Mixer pulls in audio from multiple apps, Podcasting-Record mics, skype, itunes, and more into 1 file,  Digitize your analog-tapes and vinyl into itunes, pull audio from DVD’s, and other movie files, record am/fm Radio via radioshark, pull from a mic, record player, or any other audio device.

Recording Options: Record to the MP3, AAC, AIFF and WAV audio files.

Any additional resources required to use the tool?

Only for Mac OS X.

Any hardware you choose to use is optional.

Cost and where to access:

Audio Hijack Pro License Key: $32

Audio Hijack Pro + Fission Bundle: $50

Audio Hijack Pro Test Drive: Free

What the tool does well?

Easy file organization, pass you recordings off to itunes instantly, cd burning right from the recording bin, play back your recordings with a single click. Works with hundreds of VST and Audio Unit plugins, use over 50 built-in plugins to adjust audio

What it does poorly? 

Not available for anything other than Mac OS X. Noise is overlaid on all hijackings lasting longer than ten minutes on the free version. Must restart application to sync Audio Hijack Pro and application before recording.

Links to additional outside resources:   

Download Audio Hijack Pro at rogueamoeba.com