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.
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.
Psion PDA connectivity for Linux and Unix.
A system for running Perl natively within the JVM.