Nico asked recently about the availability of chemical data as RDF. There is no so much really. Finding large amounts of Open Data in chemistry is in general a problem. Things are slowly changing, however, though it is not very apparent.
About 1.5 years ago I started a FriedFeed room Open Chemical Data where RSS feeds of new chemical data are aggregated. It started with the RSS feed from the NMRShiftDB, and later ChemPedia Substances was added (which is expected to go EOL). I was informed, however, about Dryad. It is a website that allows deposition of data published in journals, as CC0. That latter is amazing! And when they announced a new twitter feed, also noted they had a RSS feed of new data sets. I asked about feeds specific for chemistry, which prompted Ryan to set up this Yahoo Pipe.
So, Dryad is now part of the Open Chemical Data room (second item):