The Brooklyn Museum in New York has recently announced an API to allow the searching of its collection. The API is free to use, but you do need to sign up for an API key before you can use it.
There are currently three methods in the API:
which between them allow you to search the collection and return a wide variety of data about the items held.
I’ve spent a little time this weekend playing around with the new API, and have started to put together a simple Flash-based browser to allow you to search through the collection. Try it out here.