We gather all potential digital resources out there in an effort to build a comprehensive digital union catalog.
Eliminate dead ends. Users retrieve not only descriptions (metadata) about resources, they have access to the real digital resources. For instance, instead of just the catalog records of a slide collection of Van Gogh's works, users are able to view images of the actual works.
Heather Morrison has posted a lengthy list of other open access sources for librarians. (via irw)