Here a few links to software I wrote: CHICKEN
A mature compiler for the Scheme programming language, targeting C, initially started by me but now actively developed and maintained by a bunch of enthusiasts. BONES
Another Scheme compiler, targeting x86_64 systems. MA
A minimalistic variant of the Acme editor, written in Tcl/Tk. I use this for my daily work. Strand
An implementation of the "Strand" parallel Prolog dialect, as described in the book "Strand: New Concepts for Parallel Programming" by Ian Foster and Stephen Taylor.