ChemCaster, from Rich's Metamolecular, is a platform for developing web-based cheminformatics applications. The advantage of such a system is that the user does not need to install any special software, nor does the application developer need to maintain a server.
Rich invited me to take it for a spin, so I signed up for a trial account and moved quickly on to my first problem, how do I access the API through Python?
It turns out that RESTful APIs tend to have common patterns, a fact which is taken advantage of by Active Resource, a Ruby library for defining classes which directly map onto the objects implied by a RESTful API. Or something like that - I neglected to read any documentation. Instead I just took Rich's example and tried to code it up in Python using PyActiveResource (this is a documentation-free project so using it is quite exciting).