JackMix, a mixer app for jack "that looks exactly like the mixer you would use if you had to connect your analog equipment."
Small mix table (base on jack) for live performances.
JAMin is the JACK Audio Connection Kit (JACK) Audio Mastering interface. JAMin is an open source application designed to perform professional audio mastering of stereo input streams. It uses LADSPA for digital signal processing (DSP).
Ingen (formerly Om) is a modular audio processing system for GNU/Linux audio systems using the Jack audio server and LV2 or LADSPA plugins.