RasMol - Roger Sayle & Glaxo Wellcome
 
Probably the most common chemical MIME format used on the web is the PDB format which is used to describe protein (and other macro-molecule) structures. By coupling a PDB viewer, such as Rasmol, you can view PDB files that have been sent across the web. Rasmol is a freely available program for most computer systems, including the Macintosh, MS-Windows and X-Windows.

RasMol is a molecular graphics program intended for the visualization of proteins, nucleic acids and small molecules. The program is aimed at display, teaching and generation of publication quality images.  The program reads in molecular co-ordinate files and interactively displays the molecule on the screen in a variety of representations and color schemes.

See configuring Netscape for using RasMol