Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
Audio Recorder - ‘Audio Recorder’ is a small utility for recording audio.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
Audio Record Wizard - How to record streaming audio with the streaming audio recorder - Audio Record Wizard.
JACK Audio Connection Kit - JACK Audio Connection Kit|Home