Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
Mobius - Mobius is live looping open source software for the real-time creation of audio loops, with an old...
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
Loopy Pro - Loopy, the sophisticated, tactile live looper app that reinvents iPhone and iPad music making.
JACK Audio Connection Kit - JACK Audio Connection Kit|Home
Repetito - Repetito: the multichannel looper software for live performance on the PC.