ydSLitProg is an SGML DTD intended to write literate programs. It is only a prototype for now, and comes with an sgmlspl spec file which converts an ydSLitProg file into a CWEB file. A converter from ydSLitProg to FWEB is being written as well.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.