IQmol

IQmol is a free open-source molecular editor and visualization package. It offers a range of features including a molecular editor, surface generation (orbitals and densities) and animations (vibrational modes and reaction pathways).

It has been integrated with the Q-Chem quantum chemistry package and offers an intuitive environment to set up, run, and analyze Q-Chem calculations. However, it can also read and display a variety of file formats, including the widely available formatted checkpoint file.