Refer to openbabel wiki or http://www.ch.ic.ac.uk/chemime for information about common molecular file formats.
Refer to http://en.wikipedia.org/wiki/Molecule_editor and http://www.ccp14.ac.uk/solution/2d_3d_model_builders/index.html for an exhaustive list of programs for building 3d molecules. Suggested free available programs for building 3D molecules are ACD/ChemSketch (windows), Avogadro (linux), Marvin (all platforms), Ghemical (linux) NIST Chemisty webbook and Drugbank.
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