In the late nineties, I studied biomedical chemistry. I would take different career choices afterwards, but I never lost interest in the subject matter.
- Period System of the Elements (formally Extensible Periodic Table)
A free, online periodic table, covering all known elements, but also a vast amount of highly theoretical elements (from neutronium to Ennennennoctocttrioctquadpenthexnilium). As far as I know, it is the most extended periodic system in the world.
- A chemical elements vocabulary for use in Microdata, et al. Currently a work in progress.