Europeana, the new European Virtual library has a thought lab.
I'm not sure how a semantic search engine helps one "think", but it is nice to see items "organized", which is really another word for "made accessible" by other means than a taxonomy. Perhaps we will eventually find a way to make search engines work in a way that is better for humans.
Interestingly, part of the thought lab is IconClass, that I wrote about years ago. Nice to know they're still around.
My first attempts with the prototype yielded a very nice picture by Pieter Huys (1519-1584) from the collection of the Louvre. No, it's not a Jeroen Bosch, not even a contemporary (Bosch died in 1516).
It is really a shame that the resolution of the images is so low.