Perspective
Cell
Supercell:
x   y   z

Ball and Stick
Ball
van der Waals Spheres

Controls:
rotate: click+drag
zoom: scroll
translate: alt+click+drag

Load CIF file (e.g. GaN.cif)
Canvas is matched to your browser window (it may be important for phones and devices with high screen resolution like iPad 3). ChemDoodle Web Component library is used to show 3D crystal models (CIF files). See a single GaN model. CIF files from The American Mineralogist Crystal Structure Database and IZA database are used.

Open Source molecule and crystal WebGL viewers

Open Source HTML5 ChemDoodle Web Component library (155+110 kb so not large) supports Protein Data Bank (PDB), MDL Molfile (MOL) and Crystallographic Information File (CIF) format files. The site has very nice examples but unfortunately canvas has small fixed size in these demos. See also
molecule (MOL) models,
3 molecules.
    PDB models
In Firefox 11 I can make (by hand) a 7000x7000 pix image of the 1CRN molecule and save it as PNG (e.g. for posters).
GLmol - Molecular Viewer on WebGL/Javascript open-source project. It supports MOL and PDB files. See GLmol demos.
See also my tiny (~10kb) "hand made" ethanol, crystal models and valence bond demos.

WebGL examples     updated 20 Apr 2012