VSTHost - Hostprogram for VST-Plugins with ASIO-Support
Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
Cantabile - Plugin host for live performance.
Soundflower - Soundflower is a Mac OS X system extension that allows applications to pass audio to other...
Blue Cat's PatchWork - Blue Cat's PatchWork is a universal plug-ins patchbay and multi FX that can host up to 64 VST, VST3, Audio Unit or built-in plug-ins into any Digital Audio Workstation (DAW) in a single instance, with both serial and parallel routing options.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!