since you're covering Library APIs as well as external ones, have you
seen the Prism 3 linked data API?
It allows developers to pull catalogue data at search and item level
as linked data. So for example one of our customers books on art as
json: http://catalogue.library.manchester.ac.uk/items/2495904.json or
a query for web standards as rss:
People have used this for university portal integrations and iPhone
apps, so it might be of interest to you...
Senior Developer, Prism 3