Avogadro is a new, open source molecular editor for Mac, Windows, and Linux. It is an advanced molecular editor designed for cross-platform use in computational chemistry, molecular modeling, bioinformatics, materials science, and related areas. It offers flexible rendering and a powerful plugin architecture.
While still in beta, the recent 0.8 release brings general usability to viewing and editing molecules on your Mac. You can quickly export graphics to PNG, JPEG, or even POV-Ray rendering, or copy from the editor and paste a transparent PNG into programs like OmniGraffle. Avogadro supports reading from over 80 chemical file formats, courtesy of the Open Babel library.
These sorts of tools will become more and more common – Open Source, mashable, easy to use. The last paragraph says a lot about the goals.
Future plans for the Mac version of Avogadro include integration of Spotlight and QuickLook, as well as built-in scripting in Python. Work is also underway to allow copy/paste from ChemDraw and other 2D chemical drawing applications. Additional builders (e.g., for biomolecules, nanotubes, and nanoparticles) and interfaces to other computational chemistry packages are due for future versions as well.