Jmol
An interactive viewer for three-dimensional chemical structures.
... quantum chemistry programs. Files can be transferred directly from several databases, including RCSB, EDS, NCI, PubChem, and MaterialsProject. Multiple files can be loaded and compared. A rich scripting language and a well-developed web API allow easy customization of the user interface. Features include interactive animation and linear morphing. Jmol interfaces well with JSpecView for spectroscopy, JSME for 2D->3D conversion, POV-Ray for images, and CAD programs for 3D printing (VRML export).