sgml2x is a script designed to help applying a DSSSL stylesheet to an SGML or XML document. It has a couple of interesting features, such as multiple possible stylesheets per document class, easy integration of new stylesheets by adding a simple new definition file in a configuration directory (system-wide, per-user, or per-project), and automatic selection of a default stylesheet to be used. It is already set up for DocBook SGML/XML.
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.