Nyquist is a language for sound synthesis and music composition.
Relational programmable database with GUI
Simple and complete bignum/rational C library with wrappers for C++
Binary Modular DataFlow Machine (BMDFM)
Cross platform GUI for Maxima
Open Source Robot Operating System
Real-time audio synthesis engine and music programming language
A game developed by Reddit community
Lisp interpreter for the PSP + UNIX-clones.