I picked this up on ChemNet. To quote:

"Chemis3D is a Java Applet which renders virtual 3D molecular models within a Web document. It is specially designed for open interactive molecular visualization on the Internet or via an intranet.

Chemis3D is a small applet (about 30Kb) running well on any Java-enabled browser and requiring no specialized plug-in nor professional applications."

The means that web site publishers have a small java application to use in addition to the rather larger JMol.

Chemis3D claims to support Brookhaven Protein DataBank (*.pdb), MSC XMol files (*.xyz), and MDL molfiles (*.mol). The user can choose how to display the molecule (wire, balls and sticks etc.), and can read off bond lengths, angles, and torsion angles.