OpenMCL is an Open Source version of Digitool's excellent Macintosh Common Lisp (MCL) implementation, which runs on LinuxPPC and MacOS X. It features a native code compiler, multithreading support, and good ANSI CL compliance.
Retro is a clean, minimalist language with roots in Forth. It supports all major OSes in use today, and was designed to be easy to learn, use, and modify for specific needs.
A pure Python implementation of the Sane API and abstraction layer.
A geocaching query tool.