Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
MP3Juices - MP3Juices is a free mp3 search engine and tool that allows you to download unlimited mp3 files anywhere around the world.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
MP3Clan - MP3Clan is a popular web-based application that allows you to enjoy and download unlimited audio songs anytime anywhere.
JACK Audio Connection Kit - JACK Audio Connection Kit|Home
Lidarr - Lidarr is a music collection manager for downloading and organizing music libraries.