Open Babel is a project designed to pick up where Babel left off, as a
cross-platform program and library designed to interconvert between many
file formats used in molecular modeling and computational chemistry.

Features currently include:
   * A huge variety of common chemical file formats
   * Recognition of file type based on filename extension
   * SMARTS matcher
   * Flexible atom typer
   * Gasteiger partial charge calculation
   * Hydrogen addition and deletion
   * Automatic feature perception (rings, hybridization, aromaticity)
   * Multiple conformer storage within molecules
   * Command line interface development class
   * Bitvector class
   * Open-source/Free Software under the GNU General Public License
   * Cross platform (Windows, Linux, Mac OS X, SGI, Solaris, Dreamcast...)

WWW: https://openbabel.org/wiki/Main_Page