Crisp : An open-source crystal structure viewer for the Mac

Here are a few screenshots to whet your appetite - click on them to see bigger versions, and their descriptions.

Full of Cocoa-y goodness. Requires OS 10.5, Leopard.

Full source code will soon be available on GitHub

Create your own plugins using Obj-C, Python, Perl, or any other language with an Obj-C bridge

This website validates against XHTML and CSS web standards. It employs the YUI library, and FancyZoom for visual niceties.