It can be used for computational chemistry, molecular modeling, bioinformatics, materials science, and other related areas. It is compatible with GAMESS, Gaussian, Q-Chem, and MOPAC systems.
Avogadro lets you measure between atoms and bonds. You can also manipulate links and atoms individually, rotating the figure automatically and even accessing a library with pre-created models of all chemical compounds.
For Mac OS X 10.4 or later.