The Chemsketch program suite is a freeware (although proprietary) product of Advanced Chemistry Development, for drawing (and MM optimizing) molecules. It's own format (specified at http://www.acdlabs.com/servlets/UserAuth?pr=chsk_fformat - registration is required but free!) would be a very useful addition to the conversion list.
-- Zoli Fekete
C4H10 from ChemSketch