ImageJ - and Other Health Care
ChemDraw - ChemDraw - The Gold Standard for Chemical Structure Drawing and Research Publications.
Fiji - Fiji: A batteries-included distribution of ImageJ.
Avogadro - Avogadro is a free, fantastically easy to use molecule editor.
Icy - Icy is an open community platform for bioimage informatics
Gnome Chemistry Utils - The Gnome Chemistry Utils include six chemistry related programs: