Hyleos ChemFileBrowser and ChemView
   Free Windows software for working with MDL SDF files and molfiles. Includes descriptors calculation like TPSA, molecular weight, HBd and HBa.
   http://www.hyleos.net

MOLGEN
   Program for the automatic generation of constitutional isomers and combinatorial libraries, for Unix/Linux and WinNT/95. Free demo available.
   http://www.mathe2.uni-bayreuth.de/molgen4/

Marvin
   Java applets for the web developer who builds chemical internet/intranet sites. The package contains an applet for editing and visualizing molecules on a web page and one for viewing molecules on a web page.
   http://www.chemaxon.com/marvin/

Mol2Mol
   Molecule file manipulation and conversion shareware for Windows. Works with about 40 file formats. Screenshots, downloads, and purchasing information.
   http://web.interware.hu/frenzy/mol2mol/index.html

Molecule for Macintosh
   Structure editor. Especially suited for computational chemistry, supports several file formats and operations such as animations and optimizations. License fee required.
   http://www.chemie.uni-erlangen.de/ccc/hommes/molecule/